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TECHNICAL  GAS  ANALYSIS 


BATES 


LIBRARY 


UNIVERSITY  OF  CALIFORNIA 


OF 

MRS.  MARTHA  E.   HALLIDIE. 
Class 


rro^ws.»s^o*IF 


ttbe  UnJmsttial  ©as  Series. 


VOLUME  I. 


TECHNICAL  GAS  ANALYSIS, 


BY 

FRANK  H.  BATES. 


PHILADELPHIA  : 

PHILADELPHIA  BOOK  COMPANY, 

PRACTICAL,  SCIENTIFIC  AND  TECHNICAL  BOOKS, 

15  SOUTH  NINTH  STREET. 

1901. 


\° 


COPYRIGHT  BY 

FRANK  H.  BATES, 
1901. 


s 


Printed  at  the 

WlCKERSHAM  PRINTING  HOUSE, 

53  and  55  North  Queen  St., 
Lancaster,  Pa.,  U.  S.  A. 


PREFACE  TO  THE  INDUSTRIAL  GAS  SERIES. 


VOLUME  I.-TECHNICAL  GAS  ANALYSIS. 

SOMK  two  years  back  the  author  of  this  work  com- 
menced writing  articles  for  the  Journal  of  Electricity 
under  the  title  of  Industrial  Gas.  Since  that  time  these 
have  appeared  almost  continuously  and  have  been  the 
subject  of  favorable  comment.  Many  requests  for  back 
numbers,  now  out  of  print,  have  encouraged  the  author 
to  present  the  series  in  book  form,  hoping  that  they  may 
prove  of  value  to  the  engineering  fraternity,  by  affording 
a  guide  to  systematic  investigation  of  economies  in  Power 
Plants. 

The  volumes  will  probably  be  issued  in  the  following 
order : 

i. — Technical  Gas  Analysis. 

2 .  — Calorimetry . 

3. — Fuel  Economies. 

4. — The  Gas  Engine  and  its  Economies. 

5. — The  Economical  Production  of  Gas  for  Power  Uses. 

Technical  Gas  Analysis  is  intended  to  serve  as  a  guide 
in  the  selection  of  the  best  method  and  proper  apparatus 
for  use  in  making  analyses  of  gases  of  varying  composi- 
tion. 

Gas  analysis  forms  an  important  factor  in  the  work  of 
many  industrial  establishments,  enabling  the  operator  in 
many  instances  to  keep  in  constant  touch  with  the  var- 
ious changes  arising.  The  value  of  gas  analysis  is 
instanced  in  the  case  of  iron,  steel  and  glass  works,  the 
former  having  to  deal  with  blast  furnace  and  the  latter 


iv  PREFACE. 

with  producer  gases ;  in  the  case  of  steam  plants  where  flue 
gas  analysis  proves  an  aid  in  the  maintenance  of  furnace 
and  boiler  efficiency  ;  in  connection  with  gas  engine  test- 
ing, where  efficiencies  are  determined  and  losses  traced 
by  the  analysis  of  the  gases  admitted  and  exhausted ;  and 
finally  in  .  the  gas  works,  where  a  uniformity  of  product 
is  a  necessary  condition  to  successful  manufacture. 

The  book  being  written  in  a  plain  style,  well  illustrated 
by  both  sketches  and  examples  and  with  a  simple  treat- 
ment of  volume  contractions  and  chemical  reactions, 
make  it  valuable  to  the  engineer  who  has  no  knowledge 
of  chemistry  as  well  as  to  the  expert  analyst. 

In  the  preparation  of  the  following  chapters  the  present 
literature  on  the  subject  has  been  freely  consulted,  and  the 
author  would  acknowledge  his  indebtedness  to  ' '  Methods 
of  Gas  Analysis,"  by  Hempel,  in  the  treatment  of  the 
Hempel  apparatus,  in  which  the  descriptive  matter  is 
largely  as  in  the  original,  but  made  to  conform  to  the 
general  plan  of  this  work. 

FRANK  H.  BATES. 

San  Francisco,  January  31, 


CONTENTS. 


CHAPTER  I. 

COLLECTION  OF  SAMPLES. 

PAGE 

The  plain  tube  with  straight    ends  to    be  closed  by  a  blow- 

piPe I 

The  collection  tube  with  glass  stop-cocks;  Keeping  the  glass 

stop-cocks  lubricated;  Cases  for  collection  tubes;  Apparatus 
for  obtaining  average  samples  of  a  gas,  being  generated,  when 
the  composition  varies 2 

Suitable  piping  for  conducting  gases  from  furnaces;  Porcelain, 
glass,  platinum,  lead  or  rubber  tubing;  Currents  in  flue- ways; 
Getting  a  sample  representing  a  fair  average  ........  5 

Collecting  mine  gases;  Packing  used  iri  making  joints   .    .  •    .      6 

CHAPTER  II. 

METHODS  OF  GAS  ANALYSIS. 
Apparatus  to  be  used  for  the  analysis  of  furnace  or  chimney 

gas,  producer  gas,  illuminating  gas  ;  A  make-shift  apparatus.     7 
Analysis  with  this  apparatus n 

CHAPTER  III. 

THE   ORSAT  APPARATUS. 

Examination  of  furnace  or  chimney  gases  by  means  of  the 
Orsat  apparatus;  Description  of  the  Orsat  apparatus  ...  17 

Manipulation 19 

Determination  of  carbon  dioxide 21 

Of  oxygen 23 

Of  carbon  monoxide;  Of  nitrogen;  Special  hints;  precautions  as 
to  (order  of)  using  the  reagents,  draining  the  walls  of  the 
burette,  time  required  for  an  analysis,  absorbing  capacities  of 
the  reagents;  limit  of  error  with  this  apparatus  .    ......    22 

(v) 


Vi  CONTENTS 

CHAPTER  IV. 

THE  ELLIOTT  APPARATUS. 

PAGE 

Principle  of  this  apparatus;  Description 24 

Determination  of  carbon  dioxide 29 

Of  illuminants;  Of  oxygen 30 

Of  carbon  monoxide;  Treatment  of  the  residue 31 

Chemical  reactions  involved 33 

Volume  contraction     . 34 

Calculation  of  the  amounts  of  methane  and  hydrogen  from  the 
combustion    with   oxygen;    Determination    of    nitrogen    by 
difference;  Example  of  an  analysis  of  coal  gas    .               .    •    •    35 
Table  of  analyses  showing  range  of  work  to  which  this  appar- 
atus is  adapted 38 

CHAPTER  V. 
THE  HEMPEN  APPARATUS. 

When  to  use  this  apparatus;    Description   of  the 'simple  gas 

burette 39 

Operation  of  the  gas  burette 41 

The  simple  absorption  pipette 43 

The  simple  absorption  pipette  for  solid  and  liquid  reagents       .    44 
The  double  absorption  pipette;  The  double  absorption  pipette 

for  solid  and  liquid  reagents 45 

The  ethylene  pipette 48 

The  explosion  pipette 49 

The  hydrogen  generator 50 

The  explosion  pipette  with  electrodes  for  the  decomposition  of 

water    .  .52 

The  combustion  of  methane  and  hydrogen  in  a  gas  mixture 
without  explosion;  Operation  of  the  Hempel  apparatus  ...  53 

Example  of  an  analysis  of  coal  gas 57 

Special  schemes;  The  fractional  combustion  of  hydrogen  .'..'.  *6l 

The  absorption  of  oxygen  by  phosphorus 66 

Scheme  for  the  analysis  of  coal  gas  by  which  the  traces  of 
carbon  monoxide  remaining  from  the  cuprous  chloride  ab- 
sorption and  any  ethane  present  may  be  determined  ....  67 


CONTENTS  Vil 

CHAPTER  VI. 

MEASUREMENT  OF  GASES. 

PAGE 

Influence  of  pressure  on  volume .72 

Boyle's  law;  Example  illustrating  Boyle's  law 75 

Influence  of  temperature  on  volume 76 

Absolute  zero;  To  obtain  absolute  temperature;   Charles'  law; 

Example  of  Charles'  law 77 

Vapor  tension  of  liquids 79 

Effect  of  vapor  tension  on  volume 81 

Example  of  combined  corrections  for  pressure,  temperature  and 
vapor  tension;  Measurement  of  gases  over  liquids  other  than 
water;  Measurement  of  dry  gases  over  mercury;  The  expan- 
sion of  mercury 82 

CHAPTER  VIL 

PROPERTIES  OF  GASES.      PREPARATION  OF  REAGENTS  EMPLOYED. 

Properties  of  carbon  dioxide;  Of  ethylene  .        84 

Of  oxygen • 85 

Of  carbon  monoxide 86 

Of  nitrogen;  Of  hydrogen 87 

Of  methane    ...  88 

Preparation  of  potassium  hydroxide;  Of  sodium  hydroxide;  Of 
barium  hydroxide;  Of  bromine  water;  Of  potassium  pyro- 

gallate * 89 

Of  cuprous  chloride 90 

Table  I. — Tension  of  water-vapor  in  millimeters  of  mercury  for 
different  temperatures,  also  the  weights  in  grams  of  the  vapor  con- 
tained in  a  cubic  meter  of  air  when  saturated 91 

Table  II. — French  measure 93 

Table  III. — Tension  of  mercury  vapor 93 

INDEX. **,   ....    94 


CHAPTER  I.  — COLLECTION    OF   SAMPLES. 


The  method  to  adopt  in  collecting  a  gas  sample  is  de- 
pendent upon  the  conditions  under  which  one  is  operating. 
The  first  point  to  be  observed  is  to  use  such  means  as 
will  give  a  sample  representing  the  average  gas.  Often- 
times in  the  gases  to  be  sampled  there  exist  currents 
whose  composition  vary  considerably,  this  being  especially 
true  in  the  case  of  chemical  processes  and  furnace  gases. 
In  such  instances  some  ingenuity  must  be  exercised  to 
meet  the  special  conditions. 


FIGURE  1. 

For  the  retention  of  a  gas  sampel,  the  collection  tube 
shown  in  Figure  i  will  serve.  The  ends  are  made  quite 
long  and  drawn  down  to  about  two  millimeters  (TV  inch) 
internal  diameter.  They  should  be  of  about  200  cubic 
centimeters  capacity.  It  will  be  found  very  convenient 
for  transportation  to  have  a  box,  provided  with  separate 


FlGURE  2. 


compartments,  to  hold  about  a  dozen  of  these  tubes.  To 
take  a  sample  it  is  simply  necessary  to  connect,  by  a  short 
rubber  tube,  at  one  end  to  the  gas  supply,  allowing  the 
gas  to  flow  through  (the  gas  being  under  pressure)  till 
certain  that  all  air  has  been  expelled  and  that  only  pure 


2  TECHNICAL   GAS   ANALYSIS. 

gas  remains;  then  almost  stopping  the  flow  to  relieve  the 
tube  of  pressure,  seal  near  the  end  by  holding  a  lighted 
candle  to  it,  or  by  means  of  an  improvised  blowpipe  made 
by  pointing  and  nearly  closing  the  end  of  a  glass  tube, 
and  then  bending  near  the  point,  cutting  off  at  a  con- 
venient length. 

The  collection  tube  will  serve  for  a  number  of  samples 
before  becoming  so  short  as  to  make  it  necessary  to  weld 
on  new  ends. 

A  somewhat  handier  tube  is  shown  in  Figure  2,  hav- 
ing glass  stop-cocks,  which  obviates  the  necessity  of  seal- 
ing by  heat.  Although  there  is  but  little  liability  to 
leakage  with  these  tubes  when  the  ground  glass  stop-cocks 
fit  properly  and  are  kept  well  greased,  yet  the  writer  has 
made  it  a  practice,  when  obliged  to  retain  the  sample  some 
time  before  making  the  analyses,  to  cover  all  joints  and 
the  open  ends  with  sealing  wax,  which  renders  leakage 
impossible.  A  case  of  these  collection  tubes  is  shown  in 
Figure  3.  Instead  of  water  for  the  confining  liquid, 
mercury  is  often  used  when  the  previous  saturation  of  the 
water  is  inconvenient  or  for  other  reasons. 

It  is  sometimes  desirable  to  obtain  a  sample  of  a  gas 
passing  through  a  conduit  of  some  kind,  which  may  rep- 
resent the  average  gas  for  a  certain  period  of  time.  For 
such  purpose  the  apparatus  illustrated  by  Figure  4  is 
well  suited.  The  tanks  A  and  B  are  constructed  of  gal- 
vanized iron,  and  measure  some  12  inches  in  diameter 
and  1 8  inches  in  length,  one  being  slightly  longer  than 
the  other.  Bottoms  and  tops  of  the  tanks  should  be 
slightly  curved  downwards  and  upwards  respectively,  to 
render  it  possible  to  secure  complete  drainage.  At  about 
the  center  of  both  top  and  bottom  is  inserted  a  ^-inch 
gas  pipe  nipple,  the  j  oint  being  strongly  soldered,  on  which 
are  screwed  pet-cocks  for  the  tops  and  pipe  connections  to 
the  outside  for  the  bottoms,  there  being  a  rim  sufficient  to 


OF  SAMPLES. 


raise  the  tank  above  the  piping.  Pet-cocks  are  put  on 
the  lower  pipes  at  a  convenient  distance  from  the  side. 
On  the  tops  there  are  also  auxiliary  nipples  with  pet-cocks 
attached,  to  allow  of  rapid  filling. 

Operation,  The  upper  (larger)  tank  is  first  filled  with 
water  and  then  connected  to  the  gas  source  by  suitable 
means,  while  on  a  shelf  below,  and  with  its  auxiliary 
pet-cock  connected  by  rubber  tubing  to  the  outlet  from 


FIGURE  3. 


the  upper  tank,  is  placed  the  smaller  one.  By  turning  on 
the  globe  valve  a  (on  the  pipe  leading  to  the  gas  source) 
and  opening  pet-cocks  £,  d,  e  and  f,  and  with  pet-cocks  c 
and  g  closed,  allow  the  water  to  run  from  the  tank  A  into 


TECHNICAL  GAS   ANALYSIS. 


FIGURE  4. 


COLLECTION  OF  SAMPLES.  5 

tank  B,  displacing  the  air  from  the  latter  and  causing  it 
to  issue  from  the  open  pet-cock  f.  As  the  water  recedes 
from  the  tank  A,  a  partial  vacuum  is  created  which  causes 
the  gas  to  rush  in.  The  receding  water,  mingling  with 
the  inrushing  gas,  becomes  thoroughly  saturated  and  is 
used  to  fill  the  lower  tank  B.  On  the  overflow  of  water 
from  the  pet-cock  of  .the  tank  B,  pet-cocks  f  and  e  are 
closed,  and  the  tank  is  disconnected  from  the  upper  one 
(which  is  removed),  and  connected  up  to  the  gas  source 
by  attaching  the  rubber  tube  h  to  the  pet-cocky".  With 
a  long  rubber  tube  attached  to  the  outlet  pet-cock  g,  to 
serve  as  a  drain  to  the  waste  barrel,  open  the  pet-cocks/ 
and  g,  causing  the  water  to  run  from  g  and  draw  in  the 
gas  through  f.  By  adjusting  these  pet-cocks,  the  time 
taken  to  fill  the  tank  may  be  lengthened  or  shortened,  so 
that  an  average  sample  of  a  run  of  a  certain  duration 
may  be  obtained.  The  previous  saturation  of  the  water 
used  prevents  the  washing  out  of  the  soluble  constituents 
of  the  gas. 

The  kind  of  piping  to  use  for  running  into  the  furnace 
or  holder  will  depend  upon  the  temperature  and  nature  of 
the  gases.  With  a  high  temperature  iron  tubes  with 
ample  water-jacketing  should  be  employed.*  Porcelain, 
glass  or  platinum  tubes  may  also  be  used.  Where  the 
gases  are  strongly  acid  and  the  time  occupied  in  making 
the  collection  is  long,  only  glass  tubes  should  be  employed ; 
they  will  not  be  affected  by  temperatures  within  600°  C. 
At  temperatures  lower  than  300°  C. ,  lead  piping  will  be 
found  serviceable  owing  to  its  great  flexibility.  Since 
vulcanized  rubber  tends  to  absorb  the  gases,  rubber  tubing 
of  any  length  should  be  avoided. 

In  a  single  flue,  way  or  conduit  from  which  the  sample 
is  being  drawn,  there  are  often  found  currents  of  some 

*Iron  piping,  if  raised  to  a  temperature  of  redness,  may  alter  the  gas  com- 
position, since  the  oxygen  of  the  iron  oxide  (iron  rust)  will  combine  with  the 
unsatisfied  carbon  monoxide  to  form  carbon  dioxide 

\ 


6  TECHNICAL  GAS  ANALYSIS. 

strength  and  of  quite  different  composition,  necessitating, 
therefore,  the  use  of  several  branches  of  piping  to  pene- 
trate equally  all  parts  and  thus  afford  a  fair  average. 
Where  the  current  in  the  flue  way  is  strong,  a  suction 
pump  or  siphon  may  be  employed  to  advantage. 

For  collecting  gases  from  mines,  etc.,  the  form  of  tank 
shown  in  Figure  4  may  also  be  used.  For  this  purpose 
fill  with  water  and  place  in  an  upright  position  where  it  is 
desired  to  sample  the  gas.  By  opening  both  lower  and 
upper  pet-cocks  cause  the  gas  to  replace  the  water.  As 
soon  as  the  tank  empties  of  water,  close  all  pet-cocks  en* 
closing  the  sample. 

For  packing  used  in  making  tight  joints,  asbestos  is 
probably  the  best,  although,  under  certain  conditions, 
putty,  plaster  of  Paris,  or  wet  waste  may  be  used. 


CHAPTER    II.— METHODS   OF   GAS   ANALYSIS. 

Apparatus.  For  furnace  and  chimney  gases,  consisting 
principally  of  carbon  *  dioxide,  carbon  monoxide,  oxygen 
and  nitrogen,  by  far  the  most  convenient  apparatus  is  the 
Orsat,  (Fisher's  modification)  arranged  in  a  portable  case. 

For  furnace  or  chimney  gases,  producer  gas,  and  illu- 
minating gas,  where  great  accuracy  may  be  sacrificed  to 
rapidity  of  operation  and  convenience,  Elliot's  latest  mod- 
ification with  explosion  burette,  half  size,  and  arranged 
in  a  traveling  case,  is  suitable. 

For  accurate  laboratory  analysis,  use  Hempel's  appa- 
ratus. 

It  sometimes  happens  that  one  is  so  situated  as  to  make 
it  desirable  to  obtain  a  rough  estimate,  or  an  approxima- 
tion, of  the  constituents  of  a  gas,  there  being  no  standard 
apparatus  at  hand.  In  such  event,  the  tubes  illustrated 
in  Figure  5  can  be  quickly  made  up  from  plain  glass  tub- 
ing, of  about  20  millimeters*  (^  inch)  internal  diameter. 
First  bend  and  draw  out  the  projecting  end  d  of  the  tube 
A,  retaining  the  conical  form  and  making  the  external 
diameter  about  4.7  millimeters  (3/16  inch).  Make  the 
end  corrugated  so  as  to  permit  a  rubber  tube  to  be  se- 
curely fastened  thereon  by  wire,  and  have  it  project 
from  the  main  tube  some  38  millimeters  (1^2  inches) 
thus  providing  for  the  wooden  stand  ey  which  is  to  be 
slotted  to  allow  of  its  receiving  the  tube,  and  of  the  latter 
being  secured  thereto  by  a  clasp.  This  finished,  cut  the 
glass  tube  off  to  a  length  of  about  500  millimeters  (20 
inches),  and  shape  the  end  c  down  to  an  internal  diameter 

*  To  reduce  millimeters  to  inches,  multiply  by  .03937,  or  divide  by  25.4. 


TECHNICAL,  GAS  ANALYSIS. 


of  about  0.8  millimeters  (V32  inch).  Make  this  end  32 
millimeters  (1.25  inches)  in  length,  and  form  its  outside 
to  correspond  to  the  end  d  for  a  rubber  tube  connection. 
Next  make  up  the  tube  A'  of  similar  diameter  but  one- 
third  longer.  The  projection  d'  is  identical  with  d,  but 


LEVEL 

BOTTLE 


MfASURING 

BUfiSTTE- 


\ 


f-    PUBBER 

c    CONNECTION} 


COLLECTION 

TUBE- 


FIGURE  5. 

at  cf  the  tube,  instead  of  being  conically  drawn  out,  as  at 
c,  is  enlarged  to  a  funnel  shape,  forming  a  mouth  for  the 
reception  of  liquids. 

Having  this  complete,  fasten  a  piece  of  seamless  rubber 
tubing  on  the  end  c  of  the  tube  A  by  wire  ligatures,  leav- 


METHODS  OF  GAS   ANALYSIS.  tf 

ing  some  40  millimeters  (1.5  inches)  of  the  tube  length 
above  the  glass  for  the  purpose  of  inserting  a  connecting 
piece  thereon.  Fasten  the  end  of  a  piece  of  rubber  tub- 
ing one-half  meter  (19.6  inches)  long  to  the  projection 
d,  and  a  similar  piece  to  the  end  d\  connecting  the  two 
free  ends  by  a  piece  of  glass  tubing,  thereby  obviating 
the  necessity  of  removing  the  wired  ends  at  d  and  d*  when 
cleaning  the  tubes.  The  tube  A,  which  is  termed  the 
measuring  burette,  is  thus  connected  to  tube  A',  termed 
the  level-tube. 

To  calibrate  A,  proceed  as  follows :  First  ascertain  the 
amount  of  water  contained  by,  say,  325  millimeters  of 
the  length  of  the  tube  A'.  In  this  instance,  as  the  internal 
diameter  of  the  tubing  is  20  millimeters,  the  quantity 
would  be  102.102  cubic  centimeters,*  or  each  millimeter 
of  the  length  of  the  tube  would  contain  about  0.31416 
cubic  centimeters.  Now  fasten  a  thin  strip  of  paper, 
scaled  to  millimeters,  and  about  400  millimeters  in  length, 
on  the  outside  surface  of  the  tube  A',  to  serve  temporarily. 
Place  a  pinch-cock,  fy  on  the  rubber  tube  close  to  the  end 
c,  and  place  another  pinch-cock,  g,  in  a  similar  manner 
on  the  rubber  tubing  close  to  the  end  d.  With  both 
pinch-cocks  open,  fill  the  two  tubes  with  water,  having 
the  water  overflow  at  the  end  of  the  rubber  tube  c,  the 
capillary  tubing  B  not  being  attached  as  yet ;  then  close 
the  pinch-cocks  f  and  g  and  partially  empty  the  level- 
tube  A'  so  that  the  level  of  the  water  is  a  little  above 
the  lowest  reading  of  the  paper  scale.  Open  the  pinch- 
cock  g,  then  by  raising  the  level-tube  A'  so  that  the  water 
in  it  will  be  on  the  same  level  as  the  water  in  the  burette 
A  (which  is  at  the  very  top  or  end  c),  the  contents  of  both 
tubes  will  be  under  equal  pressure ;  /.  e. ,  under  equal  at- 
mospheric pressure.  Notice  at  this  time  the  reading  of 
the  water  level  in  the  level-tube  A'  on  the  improvised 

*  To  reduce  cubic  centimeters  to  cubic  inches,  divide  by  16.383. 


10  TECHNICAL   GAS   ANALYSIS. 

scale,  taking  care  to  read  the  position  of  the  lowest  point 
of  the  sharply  defined,  crescent-shaped  meniscus  formed 
at  the  surface  of  the  water. 

For  the  purpose  of  illustration,  consider  this  reading  to 
be  10  millimeters  from  the  bottom  of  the  scale.  Now 
lower  the  level  tube  A',  and  open  the  pinch-cock  f  to 
admit  air  so  as  to  allow  the  water  in  burette  A  to  drop 
about  42  millimeters  (1.6  inches)  from  its  former  level  — 
the  top  of  the  tube  at  c.  After  waiting  three  minutes  for 
the  walls  of  the  tube  to  drain,  take  the  reading  of  the 
water  level  on  the  scale  on  level-tube  A',  under  atmo- 
spheric pressure,  by  bringing  the  level  of  the  water  in 
both  tubes  to  the  same  height.  Suppose  the  reading  to 
be  20  millimeters,  then  20 — 10  (the  former  reading)  =10 
millimeters,  and  as  each  millimeter  was  found  to  contain 
0.31416  cubic  centimeters,  10  millimeters  would  equal 
10X0.31416  or  3.1416  cubic  centimeters,  the  amount  of 
air  admitted. 

Keep  the  level  of  the  liquid  in  both  tubes  at  the  same 
height  and  then  mark  the  line  of  water  level  on  the  burette 
A  with  a  file.  Now,  in  a  similar  manner  as  before,  admit 
sufficient  air  to  make  a  total  of  100  cubic  centimeters, 
which  in  the  present  case,  would  correspond  to  318.3  mil- 
limeters in  the  scale  of , the  level  tube.  In  doing  this  no 
difficulty  need  be  experienced  if  care  is  taken  to  admit 
very  little  air  as  the  required  amount  (100  cubic  centi- 
meters) is  approached.  The  level-tube  A'  should  be  raised 
frequently  to  make  the  readings  until  about  the  amount 
is  obtained  when  three  minutes  should  be  allowed  to  drain 
the  water  from  the  walls  of  the  burette  before  making  the 
final  measurement. 

Now  with  the  liquid  in  the  level-tube  A'  and  in  the 
burette  A  at  the  same  height,  mark  with  a  file  the  level  of 
the  water  in  burette  A.  This  corresponds  to  100  cubic 
centimeters,  measuring  from  the  top  at  c.  Cut  a  strip  of 


METHODS  OF  GAS  ANALYSIS.  11 

paper  of  a  length  equal  to  the  distance  between  the  two 
file  marks,  and  on  this  paper  lay  off  a  scale  in  proportion, 
divisioning  it  into  tenths  of  cubic  centimeters,  gluing  it 
on  to  the  measuring  burette  A  and  shellacking.  The  scale 
on  the  level-tube  A',  may  now  be  discarded,  and  there  has 
been  thus  improvised  an  apparatus  that,  in  lieu  of  a  bet- 
ter one,  will  suffice  for  rough  work. 

Operation.  The  pinch-cocks  f  and  g  are  first  opened 
by  simply  slipping  them  off  over  the  ends  of  the  glass 
tubes  c  and  d,  and  they  remain  so.  Water  is  poured  into 
the  mouth  c9  of  the  level-tube  A',  until  it  overflows  from 
the  short  rubber  tube  on  £,  when  the  pinch-cocks  f  and  g 
should  both  be  closed.  During  the  operation  of  filling 
with  water,  the  level-tube  A'  should  be  held  at  such  a 
height  with  respect  to  the  burette  A,  that  it  may  fill  the 
former  about  two-thirds  full.  Now  make  connection  with 
the  collection  tube  c,  containing  the  gas  sample,  by  means 
of  the  capillary  tube  ,B,  which  should  be  as  short  as  pos- 
sible and  bent  at  right  angles  at  a  point  about  30  milli- 
meters from  each  end.  In  joining  the  capillary  tube  B, 
first  prepare  it  by  filling  with  water  and  wiping  a  little 
vaseline  ovi  r  the  ends  c"  and  h"  where  the  rubber  tube 
connections  are  to  be  attached.  By  means  of  a  small 
dropping  pipette  also  fill  with  water  the  short  pieces  of 
rubber  tubing  in  the  ends  c  and  h  of  the  burette  and  col- 
lection tube  respectively,  and  by  slipping  one  end  of  the 
capillary  tube  into  the  rubber  tube  at  c  and  the  other  end 
into  the  end  of  the  rubber  tube  at  h ,  all  air  will  be  ex- 
cluded. The  end  k  of  the  collection  tube  c  should  be 
connected  by  a  piece  of  rubber  tubing  a  meter  (39.37 
inches)  long  to  the  level- bottle  D,  after  which  slip  a  pinch- 
cock  m  on  the  rubber  tube  near  k. 

The  above  connections  having  been  made,  next  place 
the  level-tube  A'  on  the  floor  with  burette  A  resting  on  a 
stand,  and  raise  the  level-bottle  D  to  a  support  arranged 


12  TECHNICAL,  GAS  ANALYSIS. 

above  the  collection  tube  c.  Open  the  pinch-cocks  g,  / 
and  m  and  the  glass-cock  j  in  the  collection  tube  c,  there- 
by putting  the  collection  tube  c  and  level-bottle  D  in  con- 
nection. By  opening  the  glass  cock  i  the  pressure  of  the 
column  of  water  between  the  collection  tube  and  the  level- 
bottle  will  force  the  gas  over  into  the  burette  A,  and  in 
this  it  will  be  assisted  by  the  expansion  of  the  water  in  A, 
due  to  the  relatively  low  position  of  level-tube  A'.  Pass 
over  about  50  cubic  centimeters  of  gas,  close  the  glass- 
cock  z",  and  agitate  the  water  in  the  burette  vigorously  in 
order  that  it  may  become  saturated  with  the  gas.  Next 
open  the  glass-cock  z*,  raise  the  level-tube  A'  and  lower 
level-bottle  D,  causing  the  gas  to  return  to  the  collection 
tube.  Agitate  the  collection  tube,  after  which  transfer 
the  gas  back  and  forth  a  few  times,  thoroughly  saturat- 
ing the  water  in  both  the  level-bottle  and  level-tube,  to  pre- 
vent the  water  washing  out  the  soluble  constituents,  of  the 
gas  when  making  the  analysis.* 

This  preliminary  operation  complete,  force  all  the  gas 
from  the  burette  A  by  raising  the  level-tube  A'  and  lower- 
ing the  level-bottle  D.  Close  the  pinch-cocks  /"and  m 
and  the  glass-cocks  i  and  /,  and  disconnect  the  rubber 
tubing  of  the  level-bottle  D  from  the  collection  tube — the 
pinch-cock  m  serving  to  prevent  the  out-flow  of  water ; 
also  remove  capillary  B  from  both  the  collection  tube  and 
burette.  Fill  the  short  rubber  tube  at  c  and  the  capillary 
tube  B  with  water,  and  after  wiping  the  ends  of  the  latter 
with  vaseline,  make  connections  with  a  new  collection 
tube,  containing  sample  gas. 

One  is  now  ready  to  proceed  with  the  analysis  proper. 

Analysis.  By  lowering  the  level-tube  and  raising  the 
level-bottle,  opening  pinch-cocks  f  and  m  and  glass-cocks 
z"  and  j,  about  103  cubic  centimeters  of  gas  is  admitted  to 

*  With  the  present  apparatus  this  is  almost  a  useless  precaution,  but  is  given 
to  familiarize  the  reader  with  principles  to  be  followed  in  more  exact  analyses. 


METHODS  OF  GAS  ANALYSIS.  13 

the  burette,  when  pinch-cock /and  glass-cocks  i  and/  are 
closed,  the  capillary  tube  disconnected,  and,  together 
with  the  collection  tube  and  level-bottle,  laid  aside.  Close 
pinch-cock  £•  and  place  level-tube  on  the  support  above, 
thereby  creating  a  pressure  due  to  the  weight  of  the  water 
column  above  the  water  level  in  the  burette.  After  wait- 
ing three  minutes  for  the  walls  of  the  burette  to  drain, 
open  pinch-cock  g  j  ust  sufficient  to  allow  the  lowest  point 
of  the  meniscus  of  the  water  to  rise  to  the  100  cubic  cen- 
timeter mark  in  the  burette,  taking  precaution  to  have 
the  eyes  on  the  same  level.  There  is  now  contained  in 
the  burette  100  cubic  centimeters  of  gas  under  pressure  a 
trifle  greater  than  atmospheric.  Open  pinch-cock  f  to 
the  air  for  but  a  moment,  thus  allowing  the  excess  pres- 
sure to  escape.  By  now  opening  pinch-cock  g  and  hold- 
ing the  level-tube  so  that  the  surface  of  the  liquid  therein 
will  be  on  the  same  level  with  the  liquid  in  the  burette, 
thus  putting  our  gas  under  atmospheric  pressure,  the  level 
in  the  burette  will  be  found  to  coincide  with  the  100  cubic 
centimeter  mark. 

In  these  illustrations,  100  cubic  centimeters  of  gas  is 
taken  to  simplify  matters,  as  the  readings  thus  give  per- 
centages direct. 

Determination  of  Carbon  Dioxide.  We  first  determine 
the  quantity  of  carbon  dioxide  (chemical  formula  CO2) 
by  absorption  with  a  reagent.*  The  reagent  used  as  an 
absorbent  may  be  potassium  hydroxide,  sodium  hydroxide, 
or  barium  hydroxide.  The  first  is  to  be  preferred,  owing 
to  its  quick  action,  but  the  last  is  employed  to  advantage 
when  the  quantity  of  carbon  dioxide  is  very  small. 

To  treat  the  gas  with  the  reagent,  lower  the  level-tube  to 
expand  the  gas  in  the  burette  until  the  level  of  the  water 

*  Most  of  the  constituents  of  coal  gas  may  be  removed  or  absorbed  by  cer- 
tain liquid  reagents,  there  being  exceptions,  however,  such  as  nydrogen, 
methane,  nrtrogen,  etc.,  which  are  removed  by  combustion. 


14  TECHNICAL,  GAS  ANALYSIS. 

lowers  almost  to  the  top  of  foot-piece  e ;  then  close  pinch- 
cock  gi  and  empty  the  level-tube  and  tubing  of  water  and 
then  partially  replace  it  with  the  absorbent.  Raise  the 
level-tube  with  the  left  hand  as  high  as  the  rubber  tubing 
permits,  when,  by  opening  pinch-cock  g>  a  considerable 
quantity,  diluted  with  the  water  left  in  the  rubber  tubing, 
will  be  forced  into  the  burette.  Lowering  and  raising  the 
level-tube  will  thoroughly  mix  the  reagent  and  the  water 
and  assist  in  the  absorption  of  the  carbon  dioxide.  By 
closing  pinch-cock  g  and  agitating  the  burette,  all  the  gas 
will  be  brought  into  intimate  contact  with  the  absorbent. 
Note  the  readings  from  time  to  time,  and  when  no  further 
diminution  of  volume  takes  place,  open  pinch-cock  g,  and 
after  waiting  three  minutes  for  the  walls  of  the  burette  to 
drain,  measure  the  gas  volume  under  atmospheric  pressure 
by  bringing  the  level  of  the  liquid  in  both  tubes  to  the 
same  height.  This  reading,  subtracted  from  100,  will 
give  the  per  cent,  by  volume  of  carbon  dioxide  in  the  gas. 

Determination  of  Illuminants.  Again  lower  the  gas 
in  the  burette  as  much  as  possible,  and  in  doing  so,  exer- 
cise the  same  care  as  before  in  order  to  prevent  the  liquid 
in  the  burette  from  dropping  too  low  lest  the  gas  gets  into 
the  tube  and  escapes.  Then  close  the  pinch-cock  g,  and 
empty  the  level-tube  of  the  reagent,  afterwards  rinsing 
out  with  water.  Next,  add  a  little  water  in  which  a  few 
drops  of  hydrochloric  acid  was  previously  mixed,  to  neu- 
tralize the  remaining  reagent  in  the  lower  portion  of  the 
burette. 

The  next  determination  is  that  of  the  illuminants  or 
heavy  hydrocarbons.  These  consist  principally  of  ethy- 
lene,  (formula  C2  H4)  the  absorbent  for  which  is  bro- 
mine water.  The  level  tube  is  nearly  filled  with  water 
and  a  little  bromine  is  added  with  a  dropping  pipette. 
The  gas  residue  is  then  treated  with  this  reagent  as  in  the 
previous  case  until  no  further  action  takes  place.  In  the 


METHODS  OF  GAS  ANALYSIS.  l5 

present  instance,  however,  before  measuring  the  amount 
of  absorption,  it  will  be  necessary  to  empty  the  level-tube 
of  the  bromine  water,  first  closing  pinch-cock  g,  and  then 
partially  replacing,  not  with  the  next  reagent,  but  with 
potassium  hydroxide,  with  which  treat  the  gas.  This  is 
necessary  after  using  bromine,  owing  to  its  high  tension, 
or  tendency  to  vaporize.  The  potassium  hydroxide  ab- 
sorbs this  vapor,  after  which  the  gas  may  be  measured 
and  the  true  percentage  of  ethylene  may  be  ascertained 
by  direct  reading. 

Determination  of  Oxygen.  Again  lowering  the  gas  in 
the  burette  and  emptying  the  level-tube,  rinse  and  parti- 
ally fill  with  potassium  pyrogallate  for  the  absorption  of 
oxygen,  (symbol  O).  The  method  of  treatment  in  this 
case  is  similar  to  the  preceding,  except  that  no  vapors  are 
formed,  and,  in  consequence,  treatment  with  potassium 
pyrogallate  alone  suffices. 

Determination  of  Carbon  Monoxide.  The  percentage 
of  oxygen  determined,  empty  the  level-tube,  rinse  with 
water,  and  add  the  next  absorbent,  cuprous  chloride,  for 
the  absorption  of  carbon  monoxide,  (formula  CO).  This 
is  our  last  determination  with  this  apparatus.  An  ex- 
ample may  serve  to  illustrate  the  foregoing  operations. 

Partial  analysis  of  Dowson  producer  gas : 

The  water  in  level-tube  and  level-bottle  was  saturated 
with  the  gas. 

From  another  collection  tube  100  cubic  centimeters  of 
the  sample  gas  was  taken  for  analysis. 

After  treating  with  potassium  hydroxide  until  no  fur- 
ther absorption  took  place,  the  gas  volume  measured  93.43 
cubic  centimeters;  hence,  100 — 93.43=6.57  cubic  centi- 
meters, the  amount  of  carbon  dioxide  in  100  cubic  cen- 
timeters of  sample  gas,  or,  carbon  dioxide  is  6.57  per  cent. 

Level-tube  emptied,  rinsed  with  water,  and  a  little 
hydrochloric  acid  added  to  neutralize  the  potassium  hy- 


16  TECHNICAL,  GAS  ANALYSIS. 

droxide.  Gas  is  treated  with  bromine  water  until  absorp- 
tion is  complete,  level-tube  then  emptied,  rinsed,  and 
partially  filled  with  potassium  hydroxide  to  absorb  the 
bromine  vapors.  Gas  volume  then  measured  93.12  cubic 
centimeters;  hence,  93.43  (last  reading)  —93.12=0.31 
cubic  centimeters,  the  amount  of  ethylene  present  in 
100  cubic  centimeters  of  sampk  gas,  or,  ethylene  is  0.31 
per  cent. 

Ivevel-tube  emptied  and  rinsed,  and  without  adding  hy- 
drochloric acid,  gas  is  treated  with  potassium  pyrogallate 
until  no  further  absorption,  and  volume  then  measured 
93.09  cubic  centimeters;  hence,  93.12  (last  reading) 
— 93.09=0.03  cubic  centimeters,  the  amount  of  oxygen 
present  in  100  cubic  centimeters  of  sample  gas,  or,  oxy- 
gen is  0.03  per  cent. 

Level-tube  emptied,  rinsed,  and  gas  treated  with  cup- 
rous chloride  until  no  further  absorption.  Gas  volume 
was  68.02  cubic  centimeters;  hence,  93.09  (last  reading) 
— 68.02=25.07  cubic  centimeters,  the  amount  of  carbon 
monoxide  present  in  100  cubic  centimeters  of  sample  gas, 
or,  carbon  monoxide  is  25.07  per  cent. 

Other  constituents  of  the  gas  could  not  be  determined 
with  this  apparatus.  They  must  be  determined  by  com- 
bustion, as  will  be  shown  later.  This  apparatus  would 
suffice,  however,  for  furnace  or  chimney  gases  composed 
of  carbon  dioxide,  oxygen,  carbon  monoxide,  and  nitro- 
gen. The  nitrogen  in  this  case  would  be  found  by  differ- 
ence; i.  e.,  by  subtracting  the  sum  of  the  other  gases 
from  100,  which  would  give  its  percentage. 


CHAPTER  III.-THE   ORSAT   APPARATUS. 


Examination  of  Furnace  or  Chimney  Gases  by  means  of 
the  Or  sat  Apparatus.  With  the  apparatus  already  consid- 
ered, the  gas  was  drawn  into  a  measuring  burette  and  suc- 
cessively treated  by  the  absorbents,  which  (in  the  case  of 
potassium  pyrogallate  and  cuprous  chloride),  owing  to 
exposure  to  the  oxygen  of  the  air  during  the  treatment, 
could  be  used  but  a  few  times  before  their  powers  of  ab- 
sorption became  exhausted. 

Orsat  devised  an  apparatus  whereby  the  reagents  are 
protected  from  the  air,  and  in  which  the  gas  itself  is 
brought  in  contact  with  the  absorbents.  It  is  only  to  be 
regretted  that  the  scope  of  the  apparatus  is  so  limited. 
It  offers,  however,  a  most  convenient  means  for  the  deter- 
mination of  carbon  dioxide,  oxygen,  and  carbon  monoxide 
by  absorption,  and  nitrogen  by  difference,  these  being  the 
gases  found  as  constituents  in  furnace  and  chimney 
analyses. 

Description.  Consists  of  three  double  pipettes,  B,  C, 
and  D,  Figure  2,  made  stationary  in  the  case  and  con- 
nected by  means  of  capillary  tubing  to  a  measuring 
burette  A,  enclosed  by  a  water  jacket.  Glass  stop-cocks 
K,  F,  and  G  close  each  pipette  to  the  main  capillary,  and 
the  glass  stop-cock  H,  thereon,  affords  an  inlet  for  air 
from  the  end  j.  A  level-bottle  i,,  provides  a  means  of 
transferring  the  gas.  To  the  rear  of  the  pipettes  B,  c, 
and  D,  and  connected  by  glass  tubing,  are  three  similar 
pipettes,  whose  ends,  s,  /,  and  /',  are  connected  by  rubber 
tubing  with  a  small,  flexible  rubber  bag,  which  acts  as  a 
seal,  preventing  the  absorption  of  oxygen  from  the  air  by 
the  reagents  in  the  pipettes.  The  water-jacket  may, 


18 


TECHNICAL  GAS   ANALYSIS. 


under  ordinary  conditions,  be  simply  filled  with  water, 
v/hich  will  tend  to  prevent  slight  changes  of  temperature 
affecting  the  gas  volume.  When  the  apparatus  is  so  sit- 
uated as  to  be  subject  to  draughts  or  sudden  changes, 


FIGURE  6. 

— although  this  should  be  avoided  when  possible — con- 
nections should  be  made  with  the  water  supply,  so  as  to 
have  a  circulation  cf  water  in  the  jacket,  which  will  se- 
cure a  fairly  even  temperature. 

Figure    6  shows  Fisher's   modification    of  the    Orsat, 


THE  ORSAT  APPARATUS. 


19 


which  is  of  small  size  and  arranged  for  convenience  in 
traveling. 

Figure  7  shows  a  slight  modification  known  as  Petri- 
zilka's,  with  one  universal  stop-cock,  dispensing  with  the 
four  small  ones. 

Manipulation.  The  level -bottle  I,  is  filled  with  pure 
water,  and  with  stop-cocks  E,  F,  and  G  closed,  and  H 


FIGURE  7. 


opened,  and  the  measuring  burette  is  partly  filled  by  rais- 
ing level-bottle  i,,  forcing  air  through  exit  J.  By  closing 
stop-cock  H  and  lowering  level-bottle  i<,  the  air  remaining 
in  the  burette  and  capillary  is  expanded,  so  that  on  opening 
stop-cock  E,  the  reagent  in  pipette  B  will  be  drawn  up  to 


20  TECHNICAL   GAS   ANALYSIS. 

a  point  just  below  the  connecting  rubber  M,  when  stop- 
cock K  is  closed  and  the  reagents  in  pipettes  C  and  D  simi- 
larly raised  to  corresponding  positions.  This  done,  open 
stop-cock  H,  and  by  raising  level-bottle  L,  force  all  the  air 
from  both  the  burette  A  and  the  capillary  tubing,  displac- 
ing by  water  which  will  overflow  from  the  end  of  capillary 
at  J,  when  close  stop-cock  H. 

Preliminary  to  the  analysis  proper,  make  connections 
with  a  collection  tube  of  sample  gas  and  the  end  j,  of  cap- 
illary tubing  of  the  apparatus,  taking  same  precautions 
as  before,  with  previous  apparatus,  to  expel  all  air  from 
the  rubber  tube  and  connecting  tube,  if  one  is  used. 
Draw  in  about  50  cubic  centimeters  of  gas  (there  is  con- 
tained 100  cubic  centimeters  from  the  stop-cock  H  in  the 
capillary  tube,  to  a  point  marked  100  cubic  centimeters 
near  the  bottom  of  the  burette,  and  the  graduations  are  in 
tenths  of  cubic  centimeters),  by  lowering  level-bottle  L. 
As  soon  as  the  gas  is  admitted,  close  stop-cock  H,  and  raise 
and  lower  the  level-bottle  to  cause  the  gas  to  come  in 
through  contact  with  the  water,  thus  saturating  the  latter 
with  the  absorbable  constituents  of  the  gas.  Open  stop- 
cock H  and  expel  the  gas,  filling  completely  the  burette  and 
capillary  with  the  saturated  water,  and  on  its  overflowing 
at  j  close  the  stop-cock  H.  We  are  now  ready  for  our  sam- 
ple for  analysis,  so  make  connections  with  a  new  collection 
tube  and  draw  in  through  end  j,  in  a  similar  manner,  a 
little  more  than  100  cubic  centimeters, — say,  for  instance, 
101  cubic  centimeters — closing  stop-cock  H  immediately 
on  securing  that  amount.  Wait  one  minute  for  the  walls 
of  the  burette  to  drain,  and  then  close  the  pinch-cock  I 
on  the  rubber  tube  connecting  the  level-bottle  and  the 
burette,  close  to  the  latter.  By  raising  the  level-bottle  L, 
a  pressure  is  created,  due  to  the  height  of  the  column  of 
water,  so  that  on  gradually  opening  the  pinch-cock  I,  the 
gas  is  forced  up  in  the  burette.  With  the  eyes  on  the 


THE  ORSAT  APPARATUS.  21 

level  of  the  100  cubic  centimeter  mark  on  the  burette, 
close  the  pinch-cock  i  just  as  the  lowest  point  of  the  me- 
niscus reaches  the  mark,  when  we  will  have  ibo  cubic 
centimeters  of  gas  at  little  more  than  atmospheric  pres- 
sure. By  opening  the  stop-cock  H  for  but  a  moment,  this 
excess  will  escape  to  the  air,  leaving  us  exactly  100  cubic 
centimeters  of  gas.  By  opening  pinch-cock  .1  and  bring- 
ing the  level;bottle  I,  to  such  position  that  the  level  of  the 
liquid  contained  corresponds  to  the  level  of  the  liquid  in 
the  burette,  wre  will  find  that  the  level  in  the  burette  will 
be  at  the  100  cubic  centimeter  mark,  proving  the  amount 
of  gas  contained  to  be  100  cubic  centimeters  at  atmospheric 
pressure. 

Determination  of  Carbon  Dioxide.  We  may  now  treat 
our  gas  to  the  first  absorbent,  potassium  l^droxide,  which 
is  contained  in  pipette  B,  Opening  stop-cock  E  and  rais- 
ing level-bottle  i,,  forces  the  reagent  down  the  front  and  up 
into  the  rear  pipette,  laying  bare  the  contained  tubes,  wet 
with  the  reagent,  thus  exposing  a  large  absorbing  surface. 
This  reagent  quickly  absorbs  the  carbon  dioxide  present 
in  the  gas,  one  passage  of  the  gas  into  the  pipette  gener- 
ally proving  sufficient.  By  raising  and  lowering  the 
level-bottle  a  few  times  all  the  gas  is  brought  into  thor- 
ough contact  with  the  absorbent,  and  can  then  be  drawn 
back  into  the  burette  for  measurement  by  lowering  the 
level-bottle  I,,  closing  stop-cock  K,  when  the  reagent  has 
ascended  to  its  former  position  close  to  the  rubber  connec- 
tion. After  waiting  one  minute  for  the  walls  of  the  bu- 
rette to  drain,  bring  the  level  of  the  liquid  in  level-bottle 
and  burette  to  the  same  height,  and  read  the  position  of 
the  lowest  point  of  the  meniscus  on  the  scale,  giving  the 
quantity  of  carbon  dioxide  absorbed.  Again  pass  the 
gas  into  the  pipette  B,  return  to  burette,  (closing  stop- 
cock K  as  before)  and  measure,  after  waiting  one  minute 
for  burette  to  drain.  See  if  this  reading  corresponds  to 


22  TECHNICAL   GAS  ANALYSIS. 

the  former,  to  make  certain  that  the  absorption  is  complete. 
This  reading,  subtracted  from  100,  the  total  volume  of 
sample  gas,  gives  the  percentage  of  carbon  dioxide. 

Determination  of  Oxygen.  The  residue,  or  gas  remain- 
ing from  the  last  absorption,  is  now  passed  into  the  second 
pipette  c,  containing  potassium  pyrogallate,  which  absorbs 
the  oxygen.  .  Before  making  the  final  measurement,  the 
operation  should  be  repeated  as  in  the  previous  case,  to 
make  certain  that  all  the  oxygen  is  absorbed.  The  time 
required  will  not  exceed  three  minutes.  In  making  the 
reading  first  allow  one  minute  for  walls  of  burette  to  drain, 
this  being  done  whenever  a  measurement  is  to  be  made. 
The  reading  in  this  case  subtracted  from  the  previous  one, 
gives  the  percentage  of  oxygen. 

Determination  of  Carbon  Monoxide.  The  residue  is  now 
passed  into  the  third  pipette  D,  containing  cuprous  chlo- 
ride, which  absorbs  the  carbon  monoxide.  A  little  more 
time  should  be  given  to  this  absorption,  which  is  some- 
what uncertain ;  say,  at  least  five  minutes.  The  resulting 
reading,  subtracted  from  the  previous  one  (with  potassium 
pyrogallate),  gives  the  percentage  of  carbon  monoxide. 

Determination  of  Nitrogen.  Adding  the  percentages  of 
carbon  dioxide,  oxygen,  and  carbon  monoxide  together, 
and  subtracting  the  total  from  100,  gives  the  percentage 
of  nitrogen  by  difference. 

Special  Hints.  In  the  foregoing  operations  always  pass 
the  gas  into  the  pipettes  in  the  order  named,  since  potas- 
sium pyrogallate,  contained  by  the  second  pipette,  will 
absorb  both  oxygen  and  carbon  dioxide ;  and  cuprous 
chloride,  of  the  third  pipette,  both  carbon  monoxide  and 
oxygen. 

Before  measuring  and  after  each  absorption,  wait  some 
stated  interval,  making  it  of  the  same  duration  through- 
out, for  the  walls  of  the  burette  to  drain  of  liquid,  since 
otherwise  the  readings  would  be  in  error. 


THE  ORSAT   APPARATUS.  23 

The  total  time  required  will  usually  be  about  twenty 
minutes  for  the  entire  analysis. 

An  accurate  account  of  the  cubic  centimeters  of  absorp- 
tion with  each  reagent  should  be  kept,  and  by  comparing 
with  the  absorbing  capacities,  one  will  constantly  know 
the  power  of  the  reagent,  so  that  he  may  renew  it  as  its 
strength  becomes  taxed. 

The  capillary  tubing  of  the  Orsat  apparatus,  shown  in 
Figure  6,  being  two  millimeters  internal  diameter,  it  re- 
quires 31.8  millimeters  of  length  (1.25  inches),  to  give 
one-tenth  of  a  cubic  centimeter..  Thus,  error  due  to  the 
reagents  not  being  exactly  on  the  mark,  will  be  slight. 

To  prevent  the  glass  stop-cocks  from  becoming  fast  in 
their  sockets,  which  often  causes  fracture  on  attempts  at 
freeing,  keep  well  lubricated  with  a  mixture  of  one  part 
tallow  and  three  parts  vaseline. 

No  trouble  need  be  experienced  in  the  use  of  this  ap- 
paratus, even  by  one  unfamiliar  with  chemical  work  or 
analysis. 


CHAPTER   IV.— THE    ELLIOTT    APPARATUS. 


By  means  of  the  apparatus  already  described,  it  was 
only  possible  to  analyze  a  mixture  of  gases  containing 
carbon  dioxide,  ethylene  (illuminants),  oxygen,  and  car- 
bon monoxide.  When  it  is  desirable  to  ascertain  the 
composition  of  a  mixture  containing  hydrogen  or  methane 
as  found  in  producer  gas,  illuminating  gas,  etc.,  recourse 
must  be  had  to  apparatus  which  affords  a  means  of 
burning  these  gases  with  oxygen,  a  measurement  of  the 
products  of  combustion,  together  with  the  contraction, 
enabling  one  to  compute  the  volumes  burned.  With  Dr. 
Elliott's  apparatus  such  a  determination  may  be  made 
very  rapidly,  although  at  the  expense  of  great  accuracy. 
Owing  to  the  explosion,  over  water,  of  the  residual  gas 
(the  portion  remaining  after  the  absorbable  constituents 
are  removed),  the  error  of  results  may  be  as  great  as  two 
per  cent.,  although  the  total  error  may  generally  be  kept 
within  one  per  cent.,  which  will  meet  the  requirements  of 
technical  work.  In  iron  and  steel  works,  metallurgical 
establishments,  for  glass-ovens,  and  regenerative  furnaces 
using  producer  gas,  and  for  the  analysis  of  chimney  or  flue 
gases,  the  * l  Elliott ' '  makes  possible  sufficiently  rapid  work 
to  enable  the  operator  to  keep  in  constant  touch  with  the 
various  changes  taking  place. 

The  principal  innovation  with  this  apparatus  lies  in  the 
treatment  of  the  gases  by  permitting  the  reagents  to  spread 
and  run  down  the  sides  of  a  long  tube  containing  the  gas 
mixture,  bringing  the  absorbent  in  intimate  contact  with 
loss  of  but  little  time. 

Description.  It  consists  of  an  absorption  tube  A  (Figure 
4),  measuring  burette  B,  and  explosion  burette  c,  all  grad- 
uated to  100  cubic  centimeters,  although  of  but  one-half 

(  24-  \ 


THE  ELUOTT  APPARATUS.  25 

the  indicated  capacity.  The  two  burettes,  B  and  c,  are 
divisioned  in  tenths  of  cubic  centimeters.  The  bulbs,  at 
the  junction  of  the  tubes  A  and  B  with  the  capillary  tub- 
ing, serve  to  render  the  apparatus  more  compact  by  lessen- 
ing the  height,  and,  in  the  case  of  the  absorption  tube  A, 
provides  a  means  of  spreading  the  liquid  reagents  used. 
At  the  lower  end  of  the  absorption  tube  A  is  inserted,  by 
means  of  a  cork  c',*  an  arm  of  capillary  tubing,  which 
communicates  by  the  three-way  stop-cock  D'  with  the 
level-bottle  M,  through  the  arm  E'  and  rubber  tubing  fast- 
ened thereon,  and  affords  an  exit  for  the  discharge  of 
reagents  by  way  of  the  arm  v.  Above  the  horizontal 
capillary  on  the  tube  A  is  a  stop-cock*  B'  communicating 
with  the  open  end  A',  ground  tapering  to  receive  the  funnel 
F'  by  which  the  reagents  are  introduced.  The  horizontal 
capillary  just  below  is  cut  off  square  at  the  ends  i'  and  j' 
to  permit  of  a  piece  of  glass  capillary  tubing  G,  being 
inserted  to  form  a  close  joint  with  a  short  piece  of  rubber 
tubing  H  holding  it  in  place.  A  similar  arrangement  is 
provided  for  the  ends  K'  and  I/,  thus  connecting  the  three 
tubes.  The  lower  ends  of  the  measuring  and  explosion 
burettes  are  drawn  out  to  receive  rubber  tubing  with 
which  to  connect  with  the  level-bottles  N  and  P.  It  is  ad- 
visable to  fasten  the  rubber  tubing  on  the  projecting  ends 
by  wire  ligatures,  necessitating  the  use  of  three  level- 
bottles,  which  is  preferable,  in  the  writer's  opinion,  to 
loose  connections  and  frequent  interchange,  as  is  the  case 
when  but  two  are  used,  as  supplied  by  the  makers. 

Near  the  lower  end  of  the  explosion  burette,  below  the 
rubber  stopper  R'  of  the  water-jacket  w,  projects  an  arm 
of  capillary  tubing  u'  with  a  stop-cock  T',  through  which 
to  introduce  the  air  and  oxygen  (or  hydrogen)  used  in 
the  ccmbustion  of  the  residual  gas.  Above  the  rubber 


*A  recent  modification,  making  the  absorption  tube  and  capillary  of  one 
piece,  does  away  with  this  cork. 


2G 


TECHNICAL   GAS   ANALYSIS. 


stopper  Q  of  the  water-jacket,  are  fused  two  platinum 
wires  p'  for  an  ignition  spark.  The  water-jacket  w  serves 
to  prevent  undue  heating  of  the  burette  during  combustion, 
saving  time  which  would  otherwise  be  required  for  its 
cooling.  As  directed  in  connection  with  the  Orsat,  when 


SEf 


« 


FIGURE  8. 


the  measuring  burette  is  subject  to  changes  of  temperature 
during  an  analysis,  it  should  also  be  water-jacketed.  The 
explosion  burette  is  made  of  heavy  glass  and  there  is  con- 
sequently but  little  liability  to  fracture  with  the  exercise 
of  proper  care  during  the  explosion. 

Pperation.     Before  commencing  an  analysis,  about  two 


THE  ELUOTT  APPARATUS.  27 

liters  (approximately  two  quarts)  of  water  should  be  sat- 
urated with  the  gas  under  examination,  to  prevent,  as  far 
as  possible,  the  washing  out  of  the  soluble  constituents  of 
the  gas  mixture,  previous  to  their  absorption  by  the  re- 
agents. With  this  apparatus  the  gas  is  successively 
treated  with  the  absorbents,  as  was  done  with  the  impro- 
vised tubes  shown  in  Figure  5,  differing  in  this  respect 
from  the  Orsat.  The  absorptions  are  made  in  the  absorp- 
tion tube  A  (Figure  8),  and  the  subsequent  measurements 
in  the  burette  B.  In  preparing  for  the  analysis  the  level- 
bottles  M,  N  and  P  are  nearly  filled  with  the  saturated 
water,  the  connections  on  the  horizontal  capillary  tubing 
between  the  ends  j'  and  i',  K'  and  i/  being  made,  stop- 
cocks D',  H'  and  M'  are  opened  to  give  a  passage  between 
the  level-bottle  M  and  absorption  tube,  and  both  through 
the  horizontal  capillary  and  into  the  measuring  and  ex- 
plosion burettes.  A  rubber  tube  should  be  fastened  on 
the  end  v  of  the  projecting  arm  from  the  stop-cock  D',  to 
carry  off  the  waste  liquids  to  the  drain. 

Open  stop-cock  B'  and  raise  all  three  level-bottles,  filling 
the  entire  apparatus  with  water,  thereby  expelling  all  air. 
Close  three-way  cock  M'  so  that  the  run  is  just  closed  to 
the  capillary,  bringing  the  outlet  up,  the  reverse  of  the 
former  position.  (In  speaking  of  three-way  stop-cocks  the 
long  or  through  passage  will  be  termed  the  "run,"  and 
the  branch  at  right  angles  to  this  the  " outlet.")  Close 
stop-cock  H'  so  that  the  run  and  outlet  are  closed  to  the 
capillary  and  measuring  burette  respectively,  with  the 
outlet  down.  Close  stop-cock  B',  taking  care  that  the  water 
overflows  at  the  end  A'.  Open  stop-cock  T'  on  the  explo- 
sion burette  to  allow  the  air,  caught  in  the  capillary 
portion,  to  escape ;  close  when  water  overflows  at  the  end 
u'.  We  are  now  ready  to  admit  the  gas  sample. 

Connection  is  made  at  end  A'  of  the  absorption  tube 
with  the  gas  source.  The  level-bottle  M  is  lowered  and 


28  TECHNICAL,  GAS   ANALYSIS. 

stop-cock  B'  opened  to  admit  a  little  more  than  100  cubic 
centimeters  of  gas.  (The  actual  amount  admitted  will  be 
a  little  more  than  50  cubic  centimeters,  inasmuch  as  all 
three  tubes  are  graduated  to  read  double  the  capacity  to 
avoid  computation  in  deriving  the  percentages.)  With 
stop-cock  B'  closed,  open  stop-cock  H'  bringing  the  outlet 
up  to  the  main  capillary,  and  the  run  up  and  down  (the 
position  shown  in  Figure  4),  when  connection  will  be 
made  between  the  absorption  tube  and  measuring  burette. 
Raise  level-bottle  M  and  lower  level-bottle  N,  causing  the 
gas  to  pass  into  the  burette.  Now  raise  the  level-bottle  N 
to  a  height  that  will  bring  the  level  of  the  water  therein 
to  the  zero  or  lowest  graduation  on  the  scale  of  the  burette 
B.  Retain  in  this  position,  and  after  waiting  one  minute  for 
the  walls  of  the  burette  to  drain,  lower  level-bottle  M  a  little, 
causing  the  water  in  the  burette  B  to  rise  to  the  zero  mark; 
then  close  stop-cock  H'  with  the  outlet  up,  when  the  burette 
will  contain  exactly  100  cubic  centimeters  of  gas  under 
atmospheric  pressure.  The  error  due  to  the  capillary 
tubing  between  the  100  cubic  centimeter  mark  and  the 
slop-cock  H'  is  of  no  consequence,  since  the  tubing  in  this 
half-sized  apparatus  is  but  one  millimeter  internal  diameter, 
requiring  127.3  millimeters  (5  inches)  of  length  to  give 
one-tenth  of  one  cubic  centimeter.  It  might  be  remarked 
here  that  any  error  consequent  upon  the  retention  of  air 
in  the  capillary  tubing,  will  be  slight,  but  may  be  readily 
estimated  by  measuring  the  length  of  the  air  bubble.  The 
gas  remaining  in  the  capillary  and  absorption  tube  may 
now  be  expelled  by  raising  level-bottle  M,  opening  stop- 
cocks H'  and  M',  to  make  connections  with  exit  N'  (having 
the  outlets  of  the  three-way  cocks  up)  and  stop-cock  B', 
closing  all  three,  on  the  overflow  of  wrater,  to  their  former 
positions.  Transfer  the  100  cubic  centimeters  of  gas  by 
raising  the  level-bottle  N,  lowering  the  level-bottle  M,  and 
opening  stop-cock  H',  so  that  it  communicates  with  the 


THE  EIvUOTr  APPARATUS.  29 

absorption  tube.  Have  the  water  rise  in  the  measuring 
burette  until  it  reaches  the  absorption  tube  end  of  the  hori- 
zontal capillary,  thus  causing  all  the  gas  to  pass  over, 
when  stop-cock  H'  is  to  be  closed,  with  outlet  up.  Place 
the  funnel  F'  on  the  end  A',  noticing  whether  there  is  any 
air  in  the  vertical  capillary ;  if  so,  it  can  be  dislodged  by 
inserting  a  copper  wire,  with  a  little  water  in  the  funnel. 
We  are  now  ready  to  treat  the  gas  with  the  reagents. 

Determination  of  Carbon  Dioxide.  The  first  determi- 
nation is,  as  in  former  instances,  that  of  the  carbon  dioxide. 
The  reagent,  potassium  hydroxide,  is  poured  into  the 
funnel  F',  filling  the  latter  about  two-thirds  full,  before 
opening  the  stop-cock  B'  just  enough  to  allow  of  the  re- 
agent spreading  evenly  around  the  bulbed  portion  of  the 
absorption  tube  A,  and  running  slowly  down  the  sides. 
Never  allow  the  reagent  in  the  funnel  to  quite  reach  the 
top  of  the  vertical  tube,  lest  air  be  admitted.  Sufficient 
of  the  potassium  hydroxide  should  be  added  to  suit  the 
requirements  of  the  gas  under  examination,  a  very  little 
sufficing  as  a  rule.  On  the  admission  of  the  proper 
amount,  close  stop-cock  B'  and  transfer  the  gas  to  the 
measuring  burette  by  opening  stop-cock  H'  and  raising 
and  lowering  level-bottles  M  and  N  respectively,  closing 
stop-cock  H'  as  soon  as  the  water  from  the  absorption  tube 
reaches  the  vertical  capillary  of  the  measuring  burette. 
Wait  one  minute  before  making  the  measurement,  for  the 
walls  of  the  burette  to  drain ;  then,  with  the  level  of  the 
water  in  the  measuring  burette  and  level 'bottle  N  at  the 
same  height,  note  the  position  of  the  lowest  point  of  the 
meniscus  at  the  surface  ot  the  water,  with  refererence  to 
the  graduations  of  the  scale.  This  gives  the  reading 
under  atmospheric  pressure,  and  subtracted  from  100,  gives 
the  amount  of  absorption.  Transfer  the  gas  to  the  ab- 
sorption tube  by  opening  stop-cock  H',  raising  level-bottle 
N  and  lowering  level-bottle  M,  and  again  treat  with  potas- 


30  TECHNICAL  GAS  ANALYSIS. 

slum  hydroxide.  Transfer  to  measuring  burette  and  take 
the  reading  under  atmospheric  pressure.  If  this  corres- 
ponds to  the  former  reading,  the  absorption  is  complete ; 
if  not,  more  reagent  must  be  added  until  two  consecutive 
readings  agree.  It  is  seldom  that  one  treatment  does  not 
suffice,  but  this  precaution  should  be  taken  after  each  ab- 
sorption. With  the  gas  in  the  measuring  burette,  turn 
the  stop-cock  D'  so  that  it  communicates  with  the  drain  v 
(position  shown  in  Figure  4);  open  stop-cock  B'  and  add 
water  through  the  funnel  F',  rinsing  all  reagent  from  the 
tube.  With  the  tube  clean,  turn  stop-cock  D'  to  shut  off 
the  drain  and  connect  the  level-bottle  and  absorption  tube; 
open  stop-cocks  H'  and  M'  to  the  horizontal  capillary,  with 
outlets  up,  and  raising  level-bottle  M,  fill  the  absorption 
tube  and  capillary  with  water,  closing  stop-cocks  M',  H' 
and  B'  as  the  water  overflows  from  the  exit  N'  and  the  end 
A'  of  the  vertical  tube.  Transfer  the  gas  to  the  absorption 
tube. 

Determination  of  Illuminants.  Fill  the  funnel  F'  two- 
thirds  full  with  water,  and  with  a  small  dropping  pipette 
add  a  few  drops  of  bromine.  Partly  open  stop-cock  B', 
allowing  the  bromine  water  to  spread  around  the  bulb  and 
flow  down  the  sides  of  the  absorption  tube.  The  tension 
of  bromine  being  high,  the  tube  will  quickly  fill  with 
vapor,  when  the  stop-cock  B'  should  be  closed.  Before 
transferring  to  the  burette  for  measurement,  add  potassium 
hydroxide  (emptying  funnel  of  any  bromine  water  remain- 
ing) to  absorb  the  bromine  vapors,  and  then  transfer  the 
gas  to  the  measuring  burette.  Note  the  reading,  which, 
subtracted  from  the  previous  one,  gives  the  percentage  of 
illuminants. 

Determination  of  Oxygen.  With  the  gas  in  the  meas- 
uring burette,  rinse  the  absorption  tube  and  capillary  well 
out  with  water  and  refill.  Transfer  the  gas  to  the  absorp- 
tion tube  and  treat  with  the  next  reagent,  potassium  py- 


THE  EI<UOTT  APPARATUS.  31 

rogallate.  Measure  the  amount  of  absorption  in  the 
measuring  burette.  This  reading,  subtracted  from  the 
last  one,  gives  the  percentage  of  oxygen. 

Determination  of  Carbon  Monoxide.  Having  rirsed 
the  absorption  tube  and  capillary  of  the  last  reagent  and 
filled  with  water,  transfer  the  gas  from  the  measuring  bu- 
rette and  treat  with  cuprous  chloride.  After  using  this, 
and  previous  to  transferring  the  gas  for  measurement,  add 
water  to  absorb  the  acid  vapors.  Transfer,  and  note  the 
reading,  which,  subtracted  from  the  last,  gives  the  per- 
centage of  carbon  monoxide.  Especial  care  should  be 
exercised  to  make  this  absorption  complete. 

The  gas  residue,  sometimes  termed  gas  rest,  or  portion 
remaining  after  the  absorbable  constituents  have  been  re- 
moved, may  consist  of  hydrogen,  methane,  and  nitrogen. 
The  explosion  or  combustion  tube  is  employed  for  their 
determination,  since  in  their  combination  wdth  oxygen 
there  is  a  resulting  contraction,  which,  together  with  the 
volume  of  carbon  dioxide  formed,  affords  sufficient  data 
for  the  computation  of  the  volume  burned. 

Operation.  The  gas  residue  is  retained  in  the  measuring 
burette;  with  the  stop-cock  H'  (Figure  8)  closed  to  the 
burette  B  and  open  to  the  horizontal  capillary,  adjust  stop- 
cock M'  so  that  it  communicates  with  the  explosion  burette, 
absorption  tube  and  outlet  N'.  By  raising  the  level-bottles 
M  and  p,  force  any  air  from  the  capillary,  completely  filling 
the  entire  apparatus  with  the  exception  of  the  measuring 
burette  containing  the  gas  residue,  with  water,  when  close 
stop-cock  M'  to  both  burette  and  capillary,  the  outlet  to- 
ward the  right.  Raise  level-bottle  N,  turn  stop-cock  H' 
so  as  to  bring  the  outlet  open  to  the  capillary  in  the  direc- 
tion of  the  explosion  burette,  lower  level-bottle  P,  open 
stop-cock  M'  so  that  it  makes  connection  between  the  ex- 
plosion and  measuring  burettes  (position  shown  in  cut), 
and  admit  to  the  former  some  15  cubic  centimeters  of  the 


32  TECHNICAL,  GAS  ANALYSIS. 

residual  gas,  by  the  graduations  on  the  explosion  burette. 
Close  stop-cock  H'  by  bringing  to  the  position  with  the 
outlet  in  the  direction  of  the  explosion  burette  just  closed, 
ar>d  after  waiting  one  minute  for  the  walls  to  drain,  raise 
level-bottle  P  so  that  the  level  of  the  contained  water  will 
correspond  to  that  in  the  explosion  burette,  and  note  the 
reading,  giving  the  volume  of  the  sample  of  residual  gas 
under  atmospheric  pressure.  Since  the  determination  of 
the  constituents  of  the  residual  gas  is  by  means  of  com- 
bustion or  chemical  union  with  oxygen,  sufficient  of  the 
latter  must  be  admitted  to  supply  the  hydrogen  and  meth- 
ane, the  nitrogen  remaining  inert.  Hydrogen  requires 
one-half  its  volume  of  oxygen  for  complete  combustion, 
and  methane  requires  twice  its  volume,  consequently,  with 
an  approximate  knowledge  of  the  amounts  of  these  con- 
stituents present,  it  is  a  simple  matter  to  decide  upon  the 
quantity  of  oxygen  required  taking  care  to  admit  in 
excess. 

With  but  a  knowledge  of  the  kind  of  gas  under  exam- 
ination, whether  coal,  water,  or  producer  gas,  etc.,  one 
will  be  sufficiently  guided  after  a  little  experience.  The  oxy- 
gen is  admitted  partly  as  free  air,  (air  is  about  22  per  cent. 
oxygen  by  volume),  and  partly  as  pure  oxygen.  Gener- 
ally speaking,  for  illuminating  gas  the  air  used  should 
equal  the  volume  of  the  gas  sample.  This  may  be  admitted 
through  the  stop-cock  T'  at  the  lower  end  of  the  explosion 
burette,  but  more  conveniently  through  the  capillary  N' 
and  stop-cock  M'  by  expanding  the  gas  in  the  explosion 
burette  by  lowering  level-bottle  p.  After  admitting  the 
air,  make  connection  between  the  end  u'  of  the  projecting 
capillary  and  the  supply  of  oxygen.*  Open  stop-cock  T', 
admitting  sufficient  oxygen  to  make  a  total  gas  volume  of 

*The  oxygen  may  be  prepared  by  heating  a  mixture  of  four  parts,  by  weight, 
of  potassium  chlorate  and  one  part  of  manganese  dioxide,  in  a  generator  sup- 
plied for  this  purpose,  and  collecting  in  a  gas  holder  in  which  the  gas  should 
be  put  under  a  slight  pressure. 


THE  ELLIOTT  APPARATUS.  33 

about  75  cubic  centimeters,  when  close  stop-cock  T'  and 
raise  and  lower  level-bottle  p,  causing  the  gas  to  become 
thoroughly  mixed,  also  dislodging  any  oxygen  caught  in 
the  capillary  above  the  stop-cock  T'.  Wait  one  minute 
for  the  burette  walls  to  drain,  then  measure  the  total  gas 
volume  under  atmospheric  pressure.  Dislodge  any  water 
adhering  to  the  ends  of  the  platinum  wires  by  tapping  the 
tube  slightly.  Lower  the  level-bottle  p  as  far  as  possible 
to  expand  the  gas,  thus  tending  to  render  the  explosion 
less  severe.  With. all  precautions  there  is  a  possibility  of 
fracture  at  this  time ;  it  is  therefore  best  not  to  expose  the 
eyes.  Make  connection  to  the  induction  coil  and  battery, 
closing  the  circuit,  causing  a  spark  to  pass  between  the 
points  of  the  wires,  thereby  igniting  the  gas,  which  gives 
a  sharp  click. 

Allow  the  heat  of  the  combustion  to  be  absorbed  by  the 
circulating  water  in  the  jacket  and  then  take  the  reading 
of  the  gas  volume  under  atmospheric  pressure.  This, 
subtracted  from  the  reading  of  total  gas  volume  taken 
before  the  explosion,  gives  the  contraction,  which,  for 
future  reference,  we  will  call  C.  Now  raise  level-bottle  p, 
lower  level-bottle  M,  and  noting  that  the  horizontal  capil- 
lary and  absorption  tube  are  filled  with  water,  transfer 
the  products  of  combustion  from  the  explosion  burette  to 
the  absorption  tube,  where  treatment  with  potassium  hy- 
droxide will  absorb  the  carbon  dioxide  formed.  After 
treatment  with  the  absorbent,  transfer  back  to  the  explo- 
sion burette,  and,  after  waiting  one  minute  for  the  walls 
of  the  burette  to  drain,  measure,  under  atmospheric  pres- 
sure, the  amount  of  absorption.  Let  the  amount,  which 
equals  the  carbon  dioxide  formed,  be  called  D.  We  now 
have  sufficient  data  to  determine  the  percentage  of  hydro- 
gen and  methane  directly,  and  the  nitrogen  by  difference. 

The  chemical  reaction  of  hydrogen  with,  oxygen  is  ex- 
pressed by  the  following  equation  : 


34  TECHNICAL  GAS   ANALYSIS. 

H2  +    (OJj   =   H,O     (Equation  i) 

Hydrogen       Oxygen  Water 

One  volume  of  hydrogen  unites  with  one-half  volume 
of  oxygen,  forming  water,  which,  in  changing  from  a 
gaseous  to  a  liquid  form,  contracts  so  as  to  be  of  no  ap- 
preciable volume,  hence  its  volume  may  be  neglected  ;  we 
have  then,  i  volume  +  y2  volume,  or  ij4  volumes  con- 
tracting to  zero  volumes ;  or,  the  amount  of  contraction 
equals  ij^  volumes,  which  is  i^  times  the  amount  of 
hydrogen  burned .  ( i  J4  H ) . 

The  reaction  of  methane  with  oxygen  is  expressed  by 
the  equation : 

CH4  +    (O2)a  =   CCX  +   2H20     (Equation  2) 

Methane         Oxygen          Carbon  Water 

Dioxide 

One  volume  of  methane  uniting  with  two  volumes  of 
oxygen,  forming  one  volume  of  carbon  dioxide  and  water. 
As  before,  the  water  volume  is  neglected,  hence  we  have 
i  volume  +  2  volumes,  or  3  volumes ;  contracting  to  i 
volume,  or  the  amount  of  contraction  equals  2  volumes, 
which  is  2  times  the  volume  of  methane  burned.  (2CH4). 
There  is  one  volume  of  carbon  dioxide  formed  for  each 
volume  of  methane  burned,  or  CO2  —  CH,. 

Collecting  from  equations  i  and  2,  we  have 

C  =    i^H  +   2CH,     (Equations) 
D  =    iCH4  (Equation  4) 

in  which  C  =  the  total  contraction  resulting  from  the 
combustion  of  the  residual  gas,  and  D  =  the  carbon  di- 
oxide formed. 

C,  the  contraction,  is  known  as  measured  in  the  explo- 
sion burette,  also  D,  the  carbon  dioxide  formed,  the  amount 
of  which  was  determined  by  absorption  with  potassium 
hydroxide ;  substituting  for  CH4  in  equation  3,  its  value 
D,  from  equation  4,  we  ha^e 


THE;  EXUOTT  APPARATUS.  35 

C  —  2D        2C  —  4D 

C  =  i^H  +  2D,  or,  H  = = (Eq.  5) 

_3_  3 

2 

By  substituting  for  D  in  equation  4,  and  for  D  and  C  in 
equation  5,  their  values,  the  per  cents  of  methane  and 
hydrogen  become  known. 

The  sum  total  of  the  per  cents  so  far  determined,  sub- 
tracted from  100,  gives  the  percentage  of  nitrogen.  An 
example  will  serve  to  illustrate  the  entire  proceeding : 

Analysis  of  Coal  Gas.  A  two-liter  bottle  of  water  was 
first  saturated  with  the  gas  to  be  examined.  The  level- 
bottles  and  apparatus  were  then  filled  with  the  prepared 
water,  expelling  all  air.  A  little  more  than  100  cubic 
centimeters  of  sample  gas  was  drawn  into  the  absorption 
tube,  and  afterward  transferred  to  the  measuring  burette, 
where  exactly  100  cubic  centimeters,  measured  under  at- 
mospheric pressure,  was  retained,  the  excess  being  expelled 
by  filling  the  apparatus  with  water  from  the  level-bottles. 

Gas  then  transferred  to  the  absorption  tube,  where  it 
was  treated  with  potassium  hydroxide,  the  first  reagent. 

Gas  returned  to  the  burette,  and,  after  waiting  one 
minute  for  drainage  of  walls,  measured  under  atmospheric 
pressure,  giving  a  reading  of  99.5.  This,  subtracted  from 
100,  gave  the  percentage  of  carbon  dioxide : 

100  —  99.5  =  0.5,  or,  CO2  =  J<£  of  i  per  cent. 

The  absorption  tube  was  drained  of  the  reagent,  rinsed, 
and  refilled  with  water.  Gas  then  transferred  to  the  ab- 
sorption tube  and  treated  with  bromine  water,  the  second 
reagent.  As  soon  as  the  absorption  was  complete,  potas- 
sium hydroxide  was  added  to  absorb  the  bromine  vapors 
formed.  Gas  then  returned  to  the  burette  and  measured 
under  atmospheric  pressure,  giving  a  reading  of  95.5. 
This,  subtracted  from  the  previous  one,  99.5,  gave  the  per 
cent,  of  illuminants : 


36  TECHNICAL  GAS   ANALYSIS. 

99.5  —  95.5  =  4,  or,  illuminants,  4  per  cent. 
The  absorption  tube  was  then  drained  of  the  reagent, 
rinsed  and  refilled  with  water. 

Gas  then  transferred  to  the  absorption  tube  and  treated 
with  potassium  pyrogallate,  the  third  reagent. 

Gas  returned  to  burette  and  measured  under  atmospheric 
pressure,  givirg  a  reading  of  95.     This,  subtracted  from 
the  previous  one,  95.5,  gave  the  percentage  of  oxygen : 
95-5  —  95  =  o-5)  or>  O  =  *4  of  i  percent. 

The  absorption  tube  was  drained  of  the  last  reagent, 
rinsed,  and  refilled  with  water. 

Gas  then  transferred  to  the  absorption  tube  and  treated 
with  cuprous  chloride,  the  fourth  reagent.  Afterwards 
water  was  added  to  absorb  the  acid  vapors  and  wash  down 
the  curdy,  white  precipitate  of  cuprous  chloride. 

Gas  returned  to  burette  and  measured  under  atmospheric 
pressure,  giving  a  reading  of  89.  This,  subtracted  from 
the  previous  one,  95,  gave  the  percentage  of  carbon 
monoxide : 

95  —  89  =  6,  or,  CO  =  6  per  cent. 

The  absorption  tube  was  drained  of  the  last  reagent, 
rinsed,  and  refilled  with  water. 

A  portion  of  the  gas  now  remaining,  termed  the  resid- 
ual gas,  was  transferred  to  the  explosion  burette,  and  on 
measuring  was  found  to  be  18  cubic  centimeters.  To  this 
was  added  about  15  cubic  centimeters  of  air  and  then 
oxygen  sufficient  to  bring  the  total  volume  to  80  cubic 
centimeters,  all  .measured  under  atmospheric  pressure.  By 
raising  and  lowering  the  level-bottle  these  gases  were 
thoroughly  mixed.  A  slight  tapping  dislodged  the  water 
adhering  to  the  points  of  the  platinum  wires.  The  gas 
mixture  was  expanded  by  lowering  the  level-bottle  as  far 
as  the  rubber  tubing  would  permit,  thereby  lessening  the 
intensity  of  the  explosion.  On  closing  the  circuit  a  sharp 


THE  EIJJOTT  APPARATUS.  3*7 

click  was  heard,  giving  assurance  that  the  explosion  oc- 
curred. 

After  a  lapse  of  three  minutes,  the  gas  was  measured 
under  atmospheric  pressure,  giving  a  reading  of  49.53. 
This,  subtracted  from  80,  the  amount  burned,  gave  the 
contraction:  80  —  49.53  =  3O-47« 

The  products  of  the  combustion,  or  gas  remaining  in 
the  explosion  burette,  was  transferred  to  the  absorption 
tube  and  treated  with  potassium  hydroxide. 

Gas  returned  to  the  explosion  burette  and  measured 
under  atmospheric  pressure,  giving  a  reading  of  41.43. 
This,  subtracted  from  the  previous  one,  49.53,  gave  the 
amount  of  carbon  dioxide  formed  by  the  combustion  of 
the  gas  residue : 

49.53  —  41.43  =  8.1,  or,  the  CO2  =  8.  i  cubic  centi- 
meters, and  CHA  present  in  18  cubic  centimeters  of  resid- 
ual gas  equals  8.1  cubic  centimeters,  since  CH4  =  D  =  CO2, 
by  equation  4. 

For  the  total  amount  of  residual  gas,  89  cubic  centime- 
ters, the  methane  would  equal,  by  simple  proportion : 

1 8  :  89  ::  8.1  :  X ;    X  =  40.05,  or,  CH4  =  40.05  per  cent. 
The  hydrogen  is  computed  from  equation  5  : 

H  =  ?c_iL_45  =  2(30.47)  -  4(3.1)  =Q5I 

or  the  hydrogen  present  in  1 8  cubic  centimeters  of  residual 
gas  equals  9.51  cubic  centimeters;  hence  for  the  total 
volume  of  residual  gas,  89  cubic  centimeters,  we  have  by 
simple  proportion 

18  :  89  ::  9.51  :  Y;     Y  =  47.02,  or  H  =  47.02  per  cent. 

All  the  constituents  of  the  sample  gas  have  now  been 
determined,  with  the  exception  of  nitrogen,  which  may 
be  found  by  difference  as  follows : 


38 


TECHNICAL  GAS  ANALYSIS. 


CO2  =    0.50 

C2H4  (illuminants)  =    4.00 

O  =    0.50 

CO  =    6.00 

CH4  =  40.05 

H  =  47.02 

Total     -     -     -    =98.07  and 
100  —  98.07  =  1.93,  or,  N  =  1.93  per  cent. 

The  following  table  of  analyses  serves  to  illustrate  the 
wide  range  of  work  to  which  this  apparatus  is  adapted : 


GASES. 

C02 

0 

CO 

N 

C2H4 

CH4 

H 

Flue  Gas  

9.6s 

8.SS 

o.oo 

81.80 

O.OO 

o.oo 

O   OO 

(Bituminous  coal) 
Hoffman  Oven  Gas. 

Producer  Gas  ...   . 

1.41 

2.  5O 

o-43 
o.  ^o 

6.49 

27.00 

0.00 

S^.^o 

2.04 
0.40 

36.31 

2.  SO 

53-32 

12    OO 

(Bituminous  coal) 
Producer  Gas  . 

2    SO 

o  ^o 

27    OO 

S7  .00 

O   OO 

1  .20 

I2.OO 

(Anthracite  coal) 
Water  Gas 

4..OO 

O.  <O 

4.S.OO 

2.OO 

o.oo 

v  so 

4S  .OO 

Natural  Gas 

o  60 

0.80 

O.6O 

^.oo 

1  .00 

72  .OO 

22.OO 

Coal  Gas 

o.  30 

O.4O 

7.60 

2.80 

4.  3O 

16.  <o 

48.10 

The  Elliott  apparatus  herein  described  is  a  modification 
of  the  older  form,  which  is  similar  except  that  it  is  not 
provided  with  an  explosion  burette  and  has  but  a  two-way 
cock  at  H',  and  no  outlet  as  at  N',  making  it  difficult  to 
expel  any  air  caught  in  the  horizontal  capillary.  This 
form  is  made  full  size,  the  burette  being  graduated  to 
contain  100  cubic  centimeters,  and  is  quite  largely  used. 


CHAPTER  V.— THE  HEMPEN  APPARATUS. 


When  it  is  desirable  to  make  an  accurate  analysis  of  a 
gas  mixture  in  the  laboratory,  and  when  time  is  not  an 
important  factor,  the  Hernpel  apparatus  affords  a  means, 
and  is,  in  consequence,  very  largely  used. 

Description.  The  simpel  gas  burette,  Figure  9,  con- 
sists of  two  glass  tubes,  A  and  A',  which  are  connected  by 
a  thin  rubber  tube  about  120  centimeters  (about  47.24 
inches)  long.  The  ends  of  the  tubing  are  simply  closed 
over  a  projecting  glass  tip  from  each  burette,  and  made 
fast  by  wrapping  tightly  with  string.  To  facilitate  the 
cleaning  of  the  burette,  the  rubber  tube  is  divided  in  the 
middle  and  the  two  ends,  R  R',  joined  together  by  a  piece 
of  glass  tubing.  Inside  the  feet,  the  tubes  A  and  A'  are 
bent  at  right  angles  and  conically  drawn  out.  They  re- 
semble, in  general  construction,  the  tubes  described  in  the 
first  number  of  these  articles.  The  tube  A  is  calibrated  so 
as  to  contain  exactly  100  cubic  centimeters  between  the 
upper  extremity  and  the  lowest  graduation,  and  is  drawn 
out  at  the  end  to  a  thick  walled  tube  my  while  the  tube  A' 
is  widened  at  the  end  to  a  mouth  h  for  the  reception  of 
liquids.  The  tube  A,  or  measuring  burette  as  it  is  termed, 
is  supplied  with  or  without  glass  stop-cocks.  A  piece  of 
rubber  tubing  over  the  end  m  may  be  closed  in  a  com- 
pletely satisfactory  manner  by  a  Mohr  pinch-cock,  fy  which 
is  put  on  close  to  the  end  of  the  capillary.  Hempel  states 
that  he  found  it  much  easier  to  make  tight  rubber  tops 
and  connections  than  perfectly  tight  glass  stop-cocks, 
wholly  aside  from  the  fact  that  by  giving  up  the  glass  cock 
the  apparatus  is  rendered  less  fragile  and  less  costly.  The 
writer  prefers  the  glass  cocks  however,  and  has  found  that 

(39) 


(40) 


FIGURE  9. 


HEMPEIv   APPARATUS.  41 

no  trouble  need  be  experienced  in  their  use  when  they  are 
kept  well  lubricated,  as  heretofore  directed.  If  pinch- 
cocks  are  used  they  must  be  removed  from  the  rubber 
tubing  after  using,  and  in  the  use  of  either  pinch-cocks 
or  glass  stop-cocks  occasional  tests  must  be  made  to  make 
certain  that  no  leakage  is  possible.  Notwithstanding  the 
fact  that  readings  cannot  be  made  under  the  rubber  tube, 
and  that  the  pinch-cock  cannot  always  be  put  on  above 
the  tube  in  exactly  the  same  positior,  no  error  results 
therefrom,  since  the  glass  tube  is  very  small.  Hempel 
found  that  differences  in  volume  are  much  less  than  one- 
tenth  of  a  cubic  centimeter,  a  variation  which,  in  deter- 
minations not  made  over  mercury,  may  be  entirely 
disregarded. 

The  graduations  on  the  measuring  burette  A  are  divided 
into  fifths  of  cubic  centimeters,  and  the  numbers  run  both 
up  and  down. 

Operation.  To  briefly  review  the  method  of  operation: 
Fill  the  tubes  A'  and  A  with  water  which  has  been  satu- 
rated with  the  gas  to  be  examined,  taking  care  to  drive 
all  air  from  the  connecting  rubber  tube,  by  suitably  rais- 
ing or  lowering  the  tubes  ;  then  join  the  burette  A  to  the 
vessel  containing  the  gas  by  means  of  a  glass  or  rubber 
tube  filled  with  water.  This  tube  is  readily  filled  by 
simply  raising  the  level-tube  A'.  To  fill  the  burette  with 
the  gas  to  be  examined,  grasp  the  tube  A'  in  the  left  hand, 
close  the  rubber  tube  at  e  by  pressing  it  between  the  little 
finger  and  palm  of  the  left  hand,  and  pour  out  the  water 
in  A'.  Place  the  level-tube  A'  on  the  floor,  and  open  the 
pinch-cock  /on  burette  A.  The  water  will  now  flow  into 
the  level-tube  A'  and  draw  the  gas  into  the  burette  A.  As 
soon  as  A  is  filled  with  gas,  close  the  pinch -cock  /,  dis- 
connect A  from  the  gas  holder,  and  after  waiting  three 
minutes  for  the  liquid  to  drain  down  the  walls  of  the  bu- 
rette, take  up  the  level-tube  A'  by  the  iron  feet,  and  by 


42 


TECHNICAL  GAS  ANALYSIS. 


raising  and  lowering  bring  the  water  in  both  tubes  to  the 
same  level.  The  gas  is  now  under  atmospheric  pressure, 
and  its  volume  is  read  off.  To  measure  off  exactly  100 
cubic  centimeters,  bring  somewhat  more  than  100  cubic 
centimeters  of  the  gas  into  the  burette,  close  the  latter 
with  the  pinch-cock  (or  glass  stop-cock),  and  let  the  water 
drain  down  for  a  period  of  three  minutes.  Now/compress 
the  gas  to  less  than  100  cubic  centimeters  by  rs^ing  the 


FIGURE  10. 


level-tube ;  close  the  rubber  tube  at  g  with  the  thumb  and 
first  finger  of  the  left  hand,  set  the  level-tube  on  the  table, 
and,  raising  the  burette  A  with  the  right  hand  to  the  level 
of  the  eyes,  carefully  open  the  rubber  tube  (held  closed 
by  the  left  hand ) ,  and  let  the  water  run  back  until  the 
meniscus  stands  at  the  ico-cubic  centimeter  mark,  when 
close  rubber  tube  again  and  open  the  pinch -cock  f  for  a 
moment,  when  the  excess  of  gas  will  escape  and  there 


THE   HEMPEL   APPARATUS. 


43 


remains  in  the  burette  exactly  100  cubic  centimeters  of 
the  gas  under  atmospheric  pressure.  The  above  directions 
illustrate  Hempel's  method  for  obtaining  a  sample  of  ex- 
actly 100  cubic  centimeters ;  the  writer  however,  would 
suggest  the  method  described  in  the  first  number  of  these 
articles  in  connection  with  the  make- 
shift apparatus,  by  which  a  little 
more  than  100  cubic  centimeters  of 
gas  is  drawn  into  the  burette,  then 
compressed  to  exactly  100  cubic 
centimeters,  when  the  excess  pres- 
sure is  relieved  by  opening  the  stop- 
cock or  pinch-cock  for  a  moment, 
thereby  giving  just  100  cubic  centi- 
meters under  atmospheric  pressure. 
The  Hempel  apparatus  provides 
a  special  pipette  for  each  reagent,  so  ^ 
designed  as  to  make  the  absorptions 
rapid  and  thorougjta,  and  yet  protect 
the  reagents  from  dilution  or  weak- 
ening by  the  absorption  of  air.  As  each  pipette  (the 
vessel  used  to  contain  the  reagent)  is  in  turn  connected 
to  the  gas  burette,  the  followirg  description  of  the  various 
pipettes  will  serve  to  familiarize  the  reader  with  their 
general  operation. 

The  simple  absorption  pipette ',  Figure  10,  consists  of 
two  large  bulbs,  b  and  ay  joined  by  the  tube  dy  and  of  a 
thick-walled  glass  tube,  n  c,  of  one-half  to 'one  millimeter 
internal  diameter,  and  bent  as  shown  in  the  figure.  This 
tube  will  be  termed  the  capillary  tube.  The  bulb  a  holds 
about  loo  cubic  centimeters  and  b  about  150  cubic  centi- 
meters, so  that  when  IGO  cubic  centimeters  of  gas  is 
brought  into  b,  sufficient  space  for  the  absorbing  liquid 
will  remain.  To  protect  the  pipette  from  being  broken 
and  to  facilitate  its  manipulation,  it  is  screwed  to  a  wooden 


FIGURE  11. 


44 


TECHNICAL    GAS    ANALYSIS. 


or  iron  standard.  Figures  10  and  n  show  the  wooden  and 
iron  supports  respectively.  On  account  of  the  different 
behavior  of  wood  or  iron  and  glass  toward  changes  of 
temperature  and  atmospheric  moisture,  it  is  advisable  to 


FIGURE  12. 


fasten  the  glass  at  only  three  places  by  means  of  metal 
bands  and  sealing  wax,  the  capillary  tube  being  allowed 
to  project  from  two  to  three  centimeters  above  the  frame. 
A  short  piece  of  rubber  tubing  is  wired  on  to  the  free  end 
of  the  capillary.  The  distance  h  (Figure  10)  must  be 
greater  than  g,  so  that  it  may  be  possible  to  enclose  a  gas 
between  two  columns  of  liquid  in  the  pipette. 

The  simple  absorption  pipette  for  solid  and  liquid  re- 
agents. The  only  difference  between  this  and  the  simple 
pipette  is  that  in  place  of  the  bulb  b  ( Figure  10),  there  is 
inserted  the  cylindrical  part  bv  (Figure  12),  which  can  be 
filled  with  solid  substances  through  the  neck  i.  A  cork 
or  rubber  stopper  k,  held  in  place  by  a  wire,  closes  the 


C   HEMPEX   APPARATUS. 


45 


FIGURE  13. 


neck.  A  glass  tube  (Figure  13) 
closed  at  the  top,  and  over  which 
a  rubber  ring,  cut  from  a  rubber 
tube  is  drawn,  makes  an  excellent 
stopper.  By  this  arrangement 
only  a  narrow  strip  of  rubber  is 
exposed  to  the  action  of  the  re- 
agent. See  Figure  13. 

The  double  absorption  pipette. 
Reagents  which  are  acted  upon 
by  oxygen  —  potassium  pyrogal- 
late,  cuprous  chloride,  ferrous 
salts,  etc. — cannot  be  kept  in  the 
aforementioned  pipettes,  since 
the  reagent  would,  in  a  short 

time,  become  inactive  through  contact  with  air.  The 
double  pipette  overcomes  this  difficulty,  permitting  the  use 
of  the  reagents  under  an  easily  movable  atmosphere  which 
is  free  from  oxygen,  and  the  reagent  employed  may  be 
kept  completely  saturated  with  those  constituents  of  the 
gas  that  it  does  not  strongly  absorb,  this  being  a  great  ad- 
vantage. The  pipette  consists  of  the  large  glass  bulb  a 
(Figure  14),  of  about  150  cubic  centimeters  capacity,  and 
three  smaller  bulbs,  b,  c  and  d,  each  containing  only  100 
cubic  centimeters.  They  are  connected  by  the  bent  tubes 
e,  f  and  g,  and  end  in  the  bent  capillary  tube  k. 

The  double  absorption  pipette  for  solid  and  liquid  re- 
agents. The  construction  may  be  easily  understood  from 
Figure  15,  and  what  has  already  been  said  in  reference  to 
the  simple  pipette  for  solid  and  liquid  reagents. 

To  prepare  the  double  pipettes  for  use,  introduce  the 
solid  substance  to  be  employed,  if  any,  and  then  fill  the 
pipette  completely  with  the  gas  to  be  analyzed  by  slowly 
drawing  the  gas  through.  Now  pour  water  through  m 
into  the  bulb  d  until  g  is  full.  Close  the  rubber  tube  / 


46  TECHNICAL,  GAS  ANALYSIS. 

with  a  pinch-cock,  insert  into  it  a  thin  glass  tube  at  least 
one  meter  long,  and  fasten  a  funnel  to  the  upper  end  of 
the  latter  by  means  of  a  piece  of  rubber  tubing.  Upon 
pouring  the  reagent  into  the  funnel,  the  pressure  due  to 
the  height  of  the  column  enables  it  to  quickly  pass  through 
the  capillary  tube  k  into  the  bulb  or  cylinder  a.  The 
action  may  be  hastened  by  gentle  suction  at  m.  After 
about  100  cubic  centimeters  of  the  reagent  has  been  in- 


FlGURE  14. 


troduced,  the  bulb  d  is  nearly  filled  with  water  and  the 
gas  remaining  in  a  is  driven  out  through  the  long  tube  by 
blowing  into  m.  The  pipette  is  now  closed  at  /  and  shaken 
for  some  time  to  remove  from  the  bulb  b  the  gases  absorb- 
able  by  the  reagent.  After  driving  out  any  gas  bubbles 
which  may  be  in  a,  suction  is  applied  at  m  and  so  much 
gas  is  sucked  out  of  the  bulb  b  that  the  liquid  in  d  will 
enter  and  fill  c.  If  the  water  first  poured  in  is  not  suf- 
ficient, more  must  be  added  from  time  to  time. 


APPARATUS. 


47 


In  pipettes  thus  prepared  the  tubes  k  and  e  and  the 
bulb  a  are  filled  with  the  aborbent,  the  space  from  b  to  f 
with  a  gas  free  from  oxygen,  c  and  g  with  water,  and  d 
with  air.  While  the  reagent  in  the  simple  pipette  may  be 
considered  to  be  saturated  with  gas  only  when  it  is  kept 
in  continual  use,  that  in  the  double  pipette  on  the  con- 
trary, remains  saturated  for  an  exceptionally  long  time, 


FIGURE  15. 


since  the  diffusion  must  take  place  through  the  confining 
100  cubic  centimeters  of  water  and  through  the  narrow 
tube.  The  error  caused  by  this  theoretical  possibility 
may  be  wholly  disregarded  in  using  the  pipette.  It  is 
possible  to  fill  the  compound  pipette  without  the  aid  of 
the  long  tube  by  manipulating  so  as  to  gradually  cause 
the  reagent  to  enter  and  then  the  water.  When  a  new 
filling  of  the  pipette  is  necessary,  the  reagent  may  easily 
be  drawn  out  by  means  of  a  rubber  pump. 

Double  absorption  pipettes  are  now  made  in  two  sections,  a  construction 
which  permits  of  easy  and  rapid  filling. 


48  TECHNICAL  GAS  ANALYSIS. 

The  ethylene  pipette.  This  is  a  special  pipette  devised 
for  use  with  sulphuric  acid  (fuming)  or  bromine  in  the 
absorption  of  ethylene  and  the  heavy  hydrocarbons  or 
fixed  illuminants.  It  consists  of  a  simple  pipette,  having 
three  bulbs  (Figure  16),  the  small  bulb  being  filled  with 
glass  beads,  which  afford  a  large  absorbing  surface  as 
with  the  Orsat  apparatus,  in  which  glass  tubes  were  used. 
With  the  use  of  sulphuric  acid,  it  is  advisable  to  use  only 
that  which  is  sufficiently  concentrated,  to  crystallize  on  a 
slight  lowering  of  temperature.  The  absorbing  power  of 
acid  of  this  strength  is  8. 

One  passage  of  the  gas  into  the  pipette  is  usually  suf- 
ficient to  effect  the  complete  absorption  of  the  ethylene 
and  heavy  hydrocarbons.  In  this  reaction  some  sulphur 
dioxide  (SCX)  is  usually  formed,  and,  moreover,  the  vapor 
of  fuming  sulphuric  acid  has  a  very  high  tension,  so  that 
the  gas  residue  before  being  measured,  must  be  freed  from 
the  acid  vapors  in  the  caustic  potash  pipette,  a  single  pas- 
sage of  the  gas  into  the  pipette  sufficing.  To  avoid  hav- 
ing the  rubber  connections  between  the  pipette  and  the 
burette  attacked  by  the  fuming  sulphuric  acid,  the  appa- 
ratus is  so  put  together  that  the  sulphuric  acid  does  not 
quite  fill  the  capillary  of  the  pipette,  and  the  connecting 
capillary  is  allowed  to  remain  empty ;  the  short  rubber 
tube  of  the  burette  is  also  freed  from  liquid  by  means  of  a 
narrow-tipped  suction  pipette,  any  reagent  remaining  in 
the  tube  being  first  washed  out  with  with  the  same  pipette. 
If  care  is  taken  that  the  sulphuric  acid  is  stopped  after 
the  absorption  at  the  same  point  in  the  capillary  at  which 
it  stood  when  the  burette  and  pipette  were  first  put  to- 
gether, then  the  small  volume  of  air  contained  in  the 
capillary  tubes  in  the  beginning  causes  no  error  in  the  de- 
termination of  the  heavy  hydrocarbons  or  other  gases, 
with  the  exception  of  nitrogen.  In  the  nitrogen  deter- 
mination, allowance  may  be  made  for  this  air  volume,  but 


THE    HEMPEL  APPARATUS. 


49 


as  each  centimeter  of  the  empty  capillary  corresponds  to 
only  0.008  cubic  centimeters,  this  value  falls  below  the 
Limit  of  unavoidable  errors.  After  the  absorption,  the 

rubber  tube  is  taken  off 
from  the  pipette,  and  the 
capillary  and  larger  tube 
are  made  air-tight  by 
closing  with  little  glass 
caps,  which  are  pushed 
over  narrow  Mohr  rings 
placed  upon  the  tube. 
For  most  purposes  the 
bromine  absorption  is  suf- 
ficiently accurate  and  far 
more  convenient.  It  is 
also  used  in  the  pipette 
just  described.  It  is  not 
necessary  to  fill  the  pi- 
pette completely  with  it, 
being  quite  sufficient  if 
a  few  cubic  centimeters 
of  bromine  lie  under 

water  in  the  pipette.  The  bromine  always  remains  below, 
there  being  a  distinct  separation  of  the  bromine  and  water 
by  reason  of  greater  specific  gravity.  The  water  above  will, 
however,  be  saturated  with  bromine  vapor  which  absorbs 
the  ethylene,  etc.  After  this  absorption,  as  in  the  case  with 
the  sulphuric  acid,  and  as  already  explained*  *in  connection 
with  the  Elliott  apparatus,  the  gas  must  be  freed  of  the 
bromine  vapor  by  passing  it  into  the  potassium  hydroxide 
pipette. 

The  explosion  pipette  consists  of  the  thick-walled  ex- 
plosion-bulb a,  Figure  17,  and  the  level-bulb  b,  which  are 
joined  together  by  a  wrapped  piece  of  rubber  tubing.    At 
c  two  fine  platinum  wires  are  fused  into  the  explosion 
d 


50 


TECHNICAL   GAS   ANALYSIS. 


pipette,  the  ends  of  the  wires  being  about  two  millimeters 
(about  V16-inch)  apart.  At  d  is  a  glass  stop-cock,  and 
the  pipette  terminates  in  tlie  capillary  e,  whose  end  is 
closed  by  a  short  piece  of  rubber  tubing  and  a  pinch-cock. 
Mercury  is  used  as  the  confining  liquid,  this  tending 
toward  greater  accuracy,  there  being  no  absorption,  with 
mercury,  of  the  carbon  dioxide  formed  by  the  combus- 
tion, as  is  the  case  when  the  explosion  is  made  over 
water,  as  with  the  Elliott  apparatus. 


The  hydrogen  generator.  When  one  is  called  upon  to 
analyze  gas  mixtures  which  do  not  contain  sufficient  com- 
bustible ingredients  to  make  them  explosive  when  mixed 
with  oxygen  or  air,  combustibility  may  be  produced  by 
adding  pure  hydrogen.  This  may  be  prepared  in  the 
special  pipette,  Figure  18.  It  is  a  compound  absorption 
pipette  which  has  two  small  bulbs  in  place  of  the  first 
large  bulb.  Through  the  tube  g  a  glass  rod  h  is  pushed 
up  to  the  mouth  of  e.  This  rod  is  fastened  tightly  into  g 


THE  HKMPKIv  APPARATUS. 


51 


by  means  of  a  piece  of  rubber  tube  slipped  over  it,  and  it 
serves  to  hold  pieces  of  chemically  pure  zinc  in  the  bulb  e. 
To  fill  the  pipette  it  is  inverted,  the  glass  rod  is  taken 
out,  and  the  pieces  of  zinc  are  dropped  into  e.  The  pipette 
is  then  closed  again,  placed  upright,  and  filled  with  di- 
luted sulphuric  acid  (1:10)  by  means  of  a  funnel  with  a 
very  long  tube  attached  to  the  capillary  i.  The  hydrogen 


FIGURE  18. 

evolved  during  the  filling  frees  the  sulphuric  acid  from 
any  absorbed  air  and  at  the  same  time  fills  the  bulbs  b 
and  c.  When  100  cubic  centimeters  of  sulphuric  acid 
have  been  brought  into  the  pipette,  some  mercury  is 
poured  into  d.  The  pipette  is  closed  at  /  with  a  piece  of 
rubber  tubing  and  a  pinch-cock.  After  a  short  time  the 
hydrogen  produced  will  drive  back  the  acid  so  that  the 


52  TECHNICAL  GAS  ANALYSIS. 

evolution  ceases ;  the  mercury  prevents  the  entrance  of 
air  into  the  apparatus,  and  pure  hydrogen  is  always  ready. 
It  is  advisable  to  force  a  little  water  into  the  capillary  tube 
i  to  prevent  the  entrance  of  air  at  this  point.  A  few  pieces 
of  platinum  foil  may  be  put  in  with  the  zinc  to  increase 
the  evolution  of  hydrogen. 

Explosion  pipette  with  electrodes  for  the  decomposition  of 
water.  A  form  of  explosion  pipette  within  which  hydro- 
gen and  oxygen  are  set  free  by  the  electrical 
decomposition  of  the  water  contained,  is 
shown  by  Figure  17.  This  is  applicable 
to  analyses  in  which  the  error  due  to  the 
explosion  being  made  over  water  will  not 
be  of  consequence.  Two  platinum  elec- 
trodes are  placed  in  the  body  of  the 
pipette,  and  some  little  distance  below 
the  line  of  the  surface  of  the  water  when 
the  gas  is  contained.  These  are  connected 
by  wires  to  a  battery.  Having  the  gas 
within  the  pipette,  the  battery  connection 
is  made,  causing  a  current  to  pass  be- 
tween the  electrodes  through  the  water, 
separating  the  latter  into  its  elementary 
constituents,  hydrogen  and  oxygen.  A 
little  practice  will  serve  to  guide  one  as 
to  the  amount  of  gas  required.  After 
disconnecting  the  battery,  connection  is 
made  with  the  sparking  wires  and  in- 
duction coil,  causing  a  spark  to  pass 
through  the  gas  mixture  and  thereby  ig- 
niting the  gases  hydrogen  and  oxygen 
FIGURE  19.  resulting  from  the  decomposition  of  the 
water.  The  generations  of  heat  and  pressure  in  connection 
therewith  is  sufficient  to  ignite  the  gas  itself,  which  ex- 


THE  HEMPEN  APPARATUS. 


53 


plodes,  giving  a  sharp  tick.  No  account  need  be  taken  of 
the  amount  of  hydrogen  and  oxygen  formed  by  the  decom- 
position of  the  water,  since  on  burning  they  return  to  the 
former  state  in  the  same  proportion. 

The  combustion  of  the  methane  and  hydrogen  in  a  gas 
mixture  may  be  effected  without  explosion,  by  bringing 
the  mixture  in  contact  with  a  wire  heated  to  redness  in  a 
pipette  similar  to  that  used  for  solid ;  see  Figure  20.  As 
this  method  offers  no 
advantage  and  re- 
quires more  time  for 
operation  than  the  ex- 
plosion pipette,  a  de- 
tailed description  will 
be  omitted. 

Operation  of  the 
Hempel  Apparatus. 
In  analyzing  a  mix- 
ture of  gases  with  this 
apparatus  the  gas  is 
successively  passed 
through  the  several 
pipettes,  simple  and 
compound,  containing 
the  reagents,  after 
which  a  portion  of  the  FIGURE  20. 

gas  residue  (portion  remaining  after  the.  absorptions 
are  complete)  may  be  passed  into  the  explosion  pipette 
and  burned  with  oxygen  to  determine  the  hydrogen, 
methane,  and  nitrogen ;  or,  for  the  latter  operation  may 
be  substituted  fractional  combustion,  in  which  case  the 
hydrogen  is  first  and  separately  removed  by  palladium, 
after  which  the  methane  is  ascertained  by  use  of  the  ex^ 
plosion  pipette. 


54  TECHNICAL  GAS   ANALYSIS. 

Manipulation  of  the  absorption  pipette.  The  measuring 
burette  b.  Figure  21,  must  first  be  filled  with  water  pre- 
viously saturated  with  the  gas  under  examination. 

The  contents  of  the  simple  pipettes  must  also  be  satu- 
rated with  the  gases  but  slightly  soluble  in  them.  The 
contents  of  the  compound  pipettes  remain  saturated  for 
an  indefinite  time  owing  to  the  enclosure  of  a  volume  of 
gas  between  two  bodies  of  liquid. 

Draw  into  the  measuring  burette  b  100  cubic  centi- 
meters of  the  gas  to  be  analyzed,  method  for  doing  which 
has  already  been  described. 

Note  that  the  reagents  of  each  pipette  are  brought  to  a 
position  close  to  the  upper  end  of  the  white  background, 
generally  found  attached  to  the  frame  of  the  pipette  and 
in  the  rear  of  the  capillary  tube.  It  would  be  advisable 
to  make  a  mark  here  (see  K,  Figure  21),  that  it  may  serve 
as  a  guide. 

Connect  the  measuring  burette  b  containing  the  100 
cubic  centimeters  of  the  gas  sample,  to  the  first  pipette  by 
means  of  the  capillary  tube  F  and  rubber  tubes  d  and  i. 
In  making  up  the  connections  with  the  capillary  tube  F, 
observe  all  the  precautions  heretofore  cited,  seeing  that 
no  air  is  permitted  to  remain  between  the  pinch-cocks  at 
d  and  i.  It  is  advisable  to  use  a  pinch-cock  at  i  as  well 
as  at  d.  To  prevent  the  enclosing  of  air,  fill  the  rubber 
tube  d  above  the  pinch-cock  with  water  by  means  of  a 
small  dropping  pipette;  then  insert  the  bent  capillary 
which  becomes  filled  with  the  water  displaced.  By  now 
compressing  that  portion  of  the  rubber  tube  i  which  is 
above  the  pinch-cock,  and  at  the  same  time  introducing 
the  free  end  of  the  capillary,  the  connection  may  be  made 
without  enclosing  air.  If,  however,  by  some  slip,  there 
should  remain  any  air  bubbles,  they  will  appear  at  the 
beginning  as  the  transfer  of  the  gas  is  made.  In  event 
of  their  not  exceeding  a  total  length  of,  say,  10  milli- 


THE;  HHMPEI*  APPARATUS. 


55 


FIGURE  21. 


56  .  TECHNICAL   GAS   ANALYSIS. 

meters  (^-inch),  in  the  upright  capillary  tube  of  the 
pipette,  they  may  be  disregarded,  since  that  would  be  in- 
dicative of  but  0.03  of  a  cubic  centimeter  or  of  an  error 
of  3/100  of  one  per  cent. 

With  the  reagent  in  pipette  at  the  mark  K,  open  the 
pinch-cocks  at  d  and  /,  having  previously  raised  the  level- 
tube  a.  Force  the  gas  into  the  pipette,  allowing  a  little 
water  to  pass  over  into  the  pipette  also,  to  make  certain 
that  the  entire  gas  volume  is  transferred.  Close  the  pinch- 
cocks  at  /  and  d  and  disconnect  the  measuring  burette 
without  removing  the  capillary  F  from  the  rubber  tube 
connections  above  the  pinch-cock  at  /.  This  leaves  the 
pipette,  containing  the  gas,  free  to  agitate,  rendering  the 
absorption  more  rapid. 

After  allowing  sufficient  time  to  elapse  to  complete  the 
absorption  of  this  constituent  of  the  gas  mixture,  the 
pipette  is  reconnected  to  the  measuring  burette,  observing 
the  same  precautions  as  regards  the  enclosing  of  air,  and 
the  gas  transferred  by  lowering  the  level-tube. 

Bring  the  reagent  to  a  position  in  the  upright  capillary 
corresponding  to  the  mark  K,  when  close  pinch-cocks  at 
i  and  d.  Measure  the  volume  of  the  gas  in  the  measuring 
burette  under  atmospheric  pressure  by  taking  the  reading 
with  the  level  of  the  liquid  in  both  level-tube  and  measur- 
ing burette  at  the  same  height. 

Subtract  this  reading  from  the  last,  and  in  this  case 
(the  first  absorption)  the  reading  is  100  cubic  centimeters, 
(the  amount  of  the  gas  mixture  taken  for  a  sample)  and 
the  result  will  be  the  cubic  centimeters  of  absorption  or 
the  percentage  of  the  constituent  absorbed.  The  per- 
centage in  each  case  will  be  slightly  in  excess  of  the  true 
absorption,  due  to  the  gas  remaining  within  the  capillary 
F,  but  this  is  hardly  to  be  considered  of  consequence, 
although  allowance  may  be  made  by  measuring  the 
capacity  of  the  bent  capillary. 


TIIK   HEMPKIv  APPARATUS.  57 


The  manipulation  of  the  compound  pipettes  is  exactly 
similar,  and  of  the  pipettes  for  solids,  the  only  difference 
lies  in  the  case  of  the  latter,  in  which  the  gas  is  exposed 
to  the  action  of  the  solid  reagent  and  requires  no  agitation 
as  is  best  done  to  quicken  the  operation  with  a  liquid  re- 
agent. By  means  of  the  Hempel  pipettes,  all  waste  is 
avoided,  the  reagents  being  used  over  and  over  again  until 
exhausted. 

After  using,  the  pipettes  are  closed  at  the  capillary  end 
by  the  insertion  of  a  short  piece  of  glass  rod  in  the  rubber 
tube  connection  z,  -releasing  the  pinch-cock  to  prevent  the 
rubber  becoming  set,  and  by  closing  the  erd  of  the  glass 
tube  h  with  a  small  cork. 

It  is  advisable  to  keep  an  accurate  account  of  the  ab- 
sorptions in  cubic  centimeters  on  the  back  of  each  pipette, 
so  that,  knowing  their  absorbing  capacity,  their  full 
strength  may  be  realized. 

By  not  allowing  any  of  the  reagent  to  run  over  into  the 
measuring  burette,  it  will  always  remain  clean;  but  should 
this  occur,  its  simple  construction  permits  of  its  being 
rinsed  without  trouble. 

An  analysis  of  coal  gas  will  serve  to  illustrate  the  use 
of  the  various  pipettes  : 

The  measuring  burette  filled  with  water  saturated  with 
the  gas  under  examination.  100  cubic  centimeters  of  gas, 
measured  under  atmospheric  pressure,  admitted  to  the 
measuring  burette. 

The  gas  transferred  from  the  measuring  burette  to  the 
first  pipette,  a  simple  pipette  containing  potassium  hy- 
droxide. After  thoroughly  agitating  the  gas  with  the 
reagent,  it  was  drawn  back  into  the  burette.  After  a 
lapse  of  three  minutes  to  allow  the  burette  walls  to  drain, 
the  volume  was  measured  and  found  to  be  99.6  cubic  cen- 
timeters. This,  subtracted  from  100  cubic  centimeters, 
gave  the  percentage  of  carbon  dioxide  : 


58.  TECHNICAL  GAS  ANALYSIS. 

100  —  99.6  =  0.4,  or  CO.  =  4/10  of  i, per  cent. 

Gas  was  passed  into  the  second  pipette,  a  special  pipette 
containing  bromine.  After  agitating,  the  gas  was  returned 
to  the  measuring  burette,  and  then,  previous  to  meas- 
uring, passed  into  the  first  or  potassium  hydroxide  pipette, 
to  remove  the  bromine  vapors.  Returned  to  measuring 
burette,  and  after  a  lapse  of  three  minutes  gas  volume 
measured  and  found  to  be  95.3  cubic  centimeters.  This, 
subtracted  from  the  last  reading,  99.6,  gave  the  percentage 
of  fixed  illuminants  or  heavy  hydrocarbons: 

99.6  —  95.3  =  4.3,  or  C,H4  =  4.3  per  cent. 

Instead  of  employing  bromine,  fuming  sulphuric  acid 
might  have  been  used  for  the  absorption  of  the  heavy 
hydrocarbons. 

The  gas  was  passed  into  the  third  pipette,  a  compound 
pipette  containing  potassium  pyrogallate.  After  agitating, 
the  gas  was  returned  to  the  measuring  burette,  and  after 
a  lapse  of  three  minutes,  gas  volume  measured  and  found 
to  be  94.8  cubic  centimeters.  This,  subtracted  from  the 
last  reading,  95.3  cubic  centimeters,  gave  the  percentage 
of  oxygen: 

95-3  —  94-8  =  °-5i  or  O  —  Y<z  of  i  per  cent. 

Instead  of  employing  potassium  pyrogallate,  phosphorus 
might  have  been  used  for  the  absorption  of  oxygen. 

The  gas  was  passed  into  the  fourth  pipette,  a  compound 
pipette  containing  ammoniacal  cuprous  chloride.  After 
thoroughly  agitating,  and  allowing  to  remain  in  contact 
with  the  reagent  some  three  minutes,  the  gas  was  returned 
to  the  measuring  burette,  and  after  a  lapse  of  three  minutes 
gas  volume  measured,  and  found  to  87.  i  cubic  centimeters. 
This,  subtracted  from  the  last  reading,  94.8  cubic  centi- 
meters, gave  the  percentage  of  carbon  monoxide: 
94.8  —  87.1  —  7.7,  or  CO  =  7.7  per  cent. 

Instead    of  employing    ammoniacal    cuprous  chloride, 


THK   HEMPEN  APPARATUS.  59  . 

cuprous  chloride  might  have  been  used  for  the  absorption 
of  carbon  monoxide,  the  former  being  required  only  when 
palladium  is  used  for  the  absorption  of  hydrogen. 

The  87.1  cubic  centimeters  of  gas  now  remaining, 
termed  the  gas  residue,  transferred  to  the  ammoniacal 
cuprous  chloride  pipette,  which  served  simply  as  a  holder. 
The  measuring  burette  thoroughly  rinsed  out  with  hydro- 
chloric acid  and  water  and  refilled  with  water  saturated 
with  air. 

A  little  of  the  gas  residue  (from  12  to  20  cubic  centi- 
meters) was  drawn  into  the  measuring  burette,  and  after 
a  lapse  of  three  minutes  gas  volume  measured,  and  found 
to  be  14.5  cubic  centimeters.  This  was  transferred  to  the 
explosion  pipette,  after  having  added  some  15  cubic  cen- 
timeters of  air,  and  oxygen  sufficient  to  bring  the  total 
volume  up  to  100  cubic  centimeters.  In  making  the 
transfer  from  the  measuring  burette,  care  was  taken  to 
have  a  little  water  pass  over,  and  the  rubber  connecting 
piece  was  closed  by  a  strong  pinch-cock  so  as  to  confine 
the  water  within  the  pipette  capillary.  A  piece  of  glass 
rod  was  also  slipped  into  the  open  end  of  the  rubber  tube 
above  the  pinch-cock  on  the  measuring  burette  being  dis- 
connected. The  pipette  was  then  thoroughly  agitated  to 
mix  the  gas,  oxygen  and  air,  the  glass  stop-cock  closed, 
and  by  connecting  to  the  induction  coil  and  battery  a 
spark  was  passed  causing  the  mixture  to  explode.  The 
glass  stop-cock  at  once  opened,  and  the  gas  transferred  to 
the  measuring  burette,  where,  after  a  lapse  of  three  min- 
utes, gas  volume  was  measured  and  found  to  be  76.05 
cubic  centimeters.  This,  subtracted  from  the  total  amount 
before  the  explosion,  100  cubic  centimeters,  the  contraction : 
100  —  76.05  =  23.95  cubic  centimeters  contraction. 

The  gas  was  now  transferred  to  the  first  pipette,  con- 
taining potassium  hydroxide,  and,  after  agitation,  returned 
to  the  measuring  burette,  where,  after  a  lapse  of  three 


60  TECHNICAL  GAS  ANALYSIS. 

minutes,  the  gas  volume  was  measured  and  found  to  be 
70.  15  cubic  centimeters.  This,  subtracted  from  the  former 
reading,  76.05  cubic  centimeters,  gave  the  carbon  dioxide 
formed,  which  is  equal  to  the  methane: 

76.05  —  70.15  =  5.90  cubic  centimeters  =  methane. 
The  gas  was  now  transferred  to  the  potassium  pyrogal- 
late  pipette,  to  make  certain  there  had  been  oxygen  in 
excess,*  and,  after  agitation,  returned  to  the  measuring 
burette.  After  a  lapse  of  three  minutes,  the  gas  volume 
was  measured  and  indicated  an  absorption  of  oxygen. 

We  now  have  all  the  data  for  the  computation  of  the 
hydrogen,  methane,  and  nitrogen. 

Methane  in  portion  of  gas  residue  exploded,  14.5  cubic 
centimeters  equaled  5.9  cubic  centimeters. 

By  proportion,  the  methane  in  the  total  gas  residue,  87.1 
cubic  centimeters,  would  equal,  therefore: 

87.1  :  14.5  ::  X  :  5.9; 
or,  X  =  35.4  ;    or,  CH,  =  35.4  per  cent. 
Hydrogen  in   portion  of  gas   residue   exploded,    14.5 
cubic  centimeters,  equaled  8.09  cubic  centimeters,  since 

2C  -  4D 
H  =  -- 

3 

in  which  H  =  hydrogen 
C  =  contraction 
D  =  methane 
the  contraction  =  23.95 

the  methane  =  5.9 
hence  by  substituting 


H  ==  2(23"95)  "         '       =  8.09 

3 

and  for  the  total  gas  residue  the  hydrogen  is  found  by 
proportion 

87.1  :  14.5  ::  Y  :  8.09; 
or,  Y  =  48.5  ;    or,  H  =  48.5  per  cent. 

*This  is  a  needless  precaution  in  our  case  since  oxygen  was  added  in  excess. 


THE   HEMPEN  APPARATUS.  61 

Tabulating  the  amounts  found: 

C02  =       0.4 

C2H4  =     4.3 

O  =     0.5 

CO  =     7.7 

H  -  48.5 

CH4  -  354 

96.8 

hence  the  nitrogen  found  by  difference  is 
100  —  96.8  =  3.2  cubic  centimeters;  or,  N  =  3.2  per  cent. 

SPECIAL  SCHEMES. 

The  Fractional  Combustion  of -Hydrogen.  By  use  of 
the  apparatus  shown  in  Figure  20  the  amount  of  hydrogen 
present  in  a  mixture  consisting  of  hydrogen,  nitrogen 
and  methane  may  be  obtained  by  direct  absorption,  the 
methane  being  subsequently  determined  by  ignition  in 
the  explosio*"  pipette,  and  the  nitrogen  by  difference.  In 
Figure  20,  a  and  b  are  the  level-tube  and  measuring  bu- 
rette respectively;  the  latter  being  connected  by  means  of 
the  capillary  K  to  a  special  tube  H,  of  about  four  milli- 
meters (5/32-inch)  internal  diameter,  and  some  20  centi- 
meters (about  8  inches)  in  length,  containing  about  four 
grains  of  palladium  sponge.  The  palladium  tube  H  is 
connected  by  another  capillary  tube,  E',  to  a  simple  pipette 
which  may  contain  water,  or,  if  preferable,  potassium 
hydroxide,  by  use  of  the  latter  avoiding  the  necessity 
of  an  extra  pipetfe.  The  pipette  serves'  as  a  receiver. 
The  beaker,  in  which  is  placed  the  tube  H,  is  nearly  filled 
with  water,  the  temperature  of  which  may  be  maintained 
at  such  a  degree  as  to  make  possible  only  the  absorption 
of  the  hydrogen. 

Operation.  After  completing  the  removal  of  all  the 
absorbable  constituents  of  the  gas  mixture  other  than 
hydrogen,  and  with  the  gas  residue  in  the  ammoniacal 


62 


TECHNICAL  GAS  ANALYSIS. 


FIGURE  22. 


THE   HEMPEI,  APPARATUS.  63 

cuprous  chloride  pipette,  draw  into  the  measuring  burette 
some  of  the  gas  residue,  and,  after  waiting  three  minutes 
for  drainage,  measure.  Join  the  burette  to  the  palladium 
tube  and  receiving  pipette  B  by  means  of  the  capillaries, 
having  previously  drawn  the  liquid  in  the  pipette  to  the 
mark  on  the  capillary  stem,  as  heretofore  directed  in  con- 
nection with  the  use  of  the  Hempel  pipette.  Bring  the 
temperature  of  the  water  in  the  beaker  to  about  95°  C., 
not  allowing  it  to  exceed  100°  C.,  nor  fall  below  90°  C. 
Open  the  pinch-cock  d,  and  by  raising  the  level-tube  a, 
force  the  gas  through  the  capillary  and  palladium  tubes 
and  into  the  pipette.  Return  the  gas  to  the  measuring 
burette  and  repeat  the  transfer  a  couple  of  times.  Replace 
the  hot  water  by  fresh  water  of  about  the  temperature  of 
the  room,  and  thoroughly  cool  the  gas  by  leading  it  back 
and  forth  through  the  palladium  tube  a  few  times. 
By  now  measuring  the  gas  volume  and  thus  determining 
the  contraction,  taking  account  of  the  air  contained  by 
the  capillary  and  the  palladium  tubes,  the  amount  of  hy- 
drogen in  the  sample  of  gas  residue  becomes  known,  since 
in  the  presence  of  the  palladium,  all  of  the  hydrogen 
unites  with  such  oxygen  (afforded  by  the  air  added)  as  is 
required  for  chemical  union.  The  product  being  water, 
two-thirds  of  the  contraction  equals  the  volume  of  hydro- 
gen, as  is  readily  seen  by  the  following 


(0.x   - 

xygen 
2  vols.  i  vol. 


Hydrogen        ,         Oxygen 


Two  volumes  of  hydrogen  unite  with  one  volume  of 
oxygen  to  form  water  possessing  no  appreciable  volume. 

Having  determined  the  hydrogen  by  the  palladium 
absorption,  draw  into  the  measuring  burette  another  por- 
tion of  the  gas  residue  from  the  ammoniac al  cuprous 
chloride  pipette;  wait  three  minutes  for  drainage  and 
measure  the  volume.  Pass  this  into  the  explosion  pipette 


64  TECHNICAL,  GAS  ANALYSIS. 

and  then  add  the  requisite  quantity  of  air  and  pure  hy- 
drogen; the  latter  is  generated  by  means  of  the  hydrogen 
pipette  already  described.*  The  gases  are  now  thoroughly 
mixed  and  ignited  by  means  of  a  spark.  The  contraction, 
due  to  combustion,  is  measured,  and  the  carbon  dioxide 
formed  is  absorbed  by  passing  the  products  of  combustion 
into  the  potassium  hydroxide  pipette.  The  absorption  is 
then  measured. 

We  now  have  sufficient  data  for  the  computation  of  the 
constituents  of  the  gas  residue. 

The  total  contraction  produced  corresponds  to: 

1.  The  hydrogen  present  in  the  original  gas  (this  is 
ascertained  by  the  palladium  absorption)  plus  one-half 
its  volume  of  oxygen,  the  quantity  requisite  for  complete 
combustion. 

2.  The  measured  quantity  of  hydrogen  added,  plus 
one-half  its  volume  of  oxygen. 

3.  The  methane  present  (equal  to  the  carbon  dioxide 
formed,  as  measured  by  the  potassium  hydroxide  absorp- 
tion) plus  two  volumes  of  oxygen  requisite  for  its  com- 
bustion. 

Knowing  the  percentages  of  both  the  hydrogen  and  the 
methane,  we  need  only  be  concerned  as  regards  the  nitro- 
gen. Its  volume  or  percentage  is  readily  found  by  adding 
the  percentages  of  all  the  other  constituents  and  subtract- 
ing the  total  from  100,  the  result  being  the  percentage  of 
nitrogen. 

It  is  not  absolutely  necessary  to  measure  the  carbon 
dioxide  formed  to  determine  the  methane;  simply  ignite 
the  mixture  of  gases  in  the  exploeion  burette,  and  then, 
without  measuring  the  contraction,  transfer  to  the  potas- 
sium hydroxide  pipette  for  the  absorption  of  the  carbon 
dioxide  formed;  after  which,  measure  the  volume  to  ascer- 

*Oxygen  may  be  used  as  heretofore  should  it  be  preferable. 


THE:  HEMPEI,  APPARATUS.  65 

tain  the  total  contraction,  which  will  equal  the  sum  of  the 
contractions  i,  2  and  3. 

Since  the  contractions  i  and  2  are  known  by  taking 
their  sum  from  the  total  contraction  (the  sum  of  i,  2  and 
3 ) ,  the  contraction  due  to  the  combustion  of  the  methane 
becomes  known,  and  thus  the  volume  and  percentage  of 
methane,  it  being  one-third  of  contraction  3.  Thus: 

Total  contraction  =C— 1+2+3 

thenC  -  (i  +  2)  =  3 

Now  methane  —  CH4 — in  burning  unites  with  two  vol- 
umes of  oxygen;  thus: 

CHt       +        (02),       =       CO,       +        (H20)2 

Methane         \  Oxygen          Carb.  Diox.       \  Water. 

i  vol.  2  vols.  i  vol. 

and  the  carbon  dioxide  being  absorbed  previous  to  meas- 
uring the  contraction,  gives  a  contraction  due  to  methane 
of  three  volumes  for  each  volume  burned,  hence  one-third 
of  the  contraction  ( 3 )  equals  the  volume  of  methane. 

It  is  not  even  necessary  to  trouble  to  make  the  absorp- 
tion of  the  carbon  dioxide  formed  with  potassium  hy- 
droxide, since  in  this  case  the  volume  of  carbon  dioxide 
formed  by  the  combustion,  remaining  unabsorbed,  lessens 
the  contraction  by  one  volume  for  every  volume  of  methane 
burned;  hence  the  volume  of  methane  will  in  this  case 
become  one-half  of  the  contraction  due  to  1  he  combustion 
of  the  methane. 

Conditions  to  be  observed  in  connection  with  the  ab- 
sorption of  hydrogen  by  means  of  palladium: 

In  a  gas  mixture,  the  carbon  dioxide,  heav}7  hydrocar- 
bons, oxygen,  carbon  monoxide,  etc.,  must  first  be  as 
completely  removed  as  is  possible  by  absorption  with  re- 
agents. For  the  absorption  of  carbon  monoxide  only 
ammoniacal  cuprous  chloride  may  be  used,  since  the  acid 
fumes  of  the  cuprous  chloride  would  tend  to  unite  with 
the  oxygen  of  the  palladium  oxide  more  readily  than 


66  TECHNICAL  GAS  ANALYSIS. 

hydrogen,  and  in  burning  not  develop  sufficient  heat  to 
make  possible  the  occlusion  of  the  hydrogen.  On  the 
other  hand,  traces  of  ammonia  do  not  interfere.  Carbon 
monoxide  or  large  quantities  of  benzole  vapor  or  vapor 
of  alcohol  do  interfere,  owing,  as  in  the  case  of  hydro- 
chloric acid,  to  their  greater  affinity  for  palladium  oxide, 
and,  in  consequence,  every  care  should  be  exercised  to 
remove  them  as  far  as  possible. 

Palladium  black  is  even  stronger  in  its  action  than 
oxydized  palladium  sponge.  It  is  made  by  reducing  pal- 
ladium chloride  with  alcohol  in  a  strongly  alkaline  solu- 
tion. It  is  probably  a  mixture  of  metallic  palladium  with 
palladium  oxide. 

The  palladium  may  be  regenerated  by  plunging  the 
tube  into  hot  water  and  passing  a  current  of  dry  air 
through  it.  The  palladium  should  always  be  kept  as  dry 
as  possible. 

The  Absorption  of  -Oxygen  by  Phosphorus.  The  em- 
ployment of  moist  phosphorus  as  an  absorbent  of  oxygen 
is  by  far  preferable  to  the  use  of  potassium  pyrogallate, 
but  this  method  is  not  universally  applicable.  The  ab- 
sorption is  carried  on  in  a  simple  pipette  for  solids,  thin 
sticks  of  phosphorus  being  inserted  in  the  bulbed  portion 
and  surrounded  by  water,  which  recedes  on  the  gas  being 
forced  in,  thus  affording  a  fresh,  bright  surface  of  phos- 
phorus for  each  absorption.  The  moist  surface  of  the 
phosphorus  rapidly  absorbs  the  oxygen,  forming  phos- 
phoric and  phosphorus  acid,  both  of  which  are  dissolved 
by  the  water  present.  The  temperature  of  the  pipette 
should  be  held  at  from  18°  to  20°  C.,  (64°  to  68°  F.). 
About  ten  minutes  should  be  allowed  this  absorption. 

The  following  conditions  should  be  observed  in  con- 
nection with  the  employment  of  phosphorus: 

The  oxygen  in  the  gas  should  not  exceed  50  per  cent. 


THE  HEMPEN  APPARATUS.  67 

The  gas  should  be  free  from  ammonia,  ethylene  and 
all  hydrocarbons,  vapor  of  alcohol,  ether,  and  etherial 
oils. 

It  is  owing  to  the  fact  that  phosphorus  is  not  acted 
upon  by  oxygen  except  the  latter  is  diluted  with  other 
gas,  that  one  should  not  have  it  present  in  greater  quan- 
tity than  50  per  cent.  In  gases  rich  in  oxygen  it  is  easy 
to  dilute  with  nitrogen  to  permit  of  the  absorption. 

During  the  reaction,  a  bright  glowing  of  the  phosphorus 
takes  place,  and  the  termination  of  the  oxidation  is  sharply 
shown  by  its  disappearance  on  the  exhaustion  of  the  oxy- 
gen. The  glow  is  only  visible  in  a  dark  room.  The 
phosphorus  may  be  repeatedly  used  but  should  be  pro- 
tected from  the  light  when  not  in  use.  The  confining 
water  surrounding  the  phosphorus  should  be  renewed 
occasionally  to  prevent  saturation  and  allow  of  the  pro- 
ducts of  combustion  or  oxidation  being  readily  absorbed, 
and  in  this  way  keeping  the  surface  of  the  phosphorus 
always  bright  and  active. 

Scheme  for  the  Analysis  of  Coal  Gas  by  which  the  traces 
of  carbon  monoxide  remaining  from  the  cuprous  chloride 
absorption,  and  any  ethane  present,  may  be  determined. 

The  writer  has  found,  that  even  with  the  exercise  of 
considerable  care,  there  remains  some  carbon  monoxide 
after  the  cuprous  chloride  absorption;  and  further,  that 
there  is  generally  present  in  the  gas  residue  traces,  at 
least,  of  ethane  (C,H6).  He  has  accordingly  arranged 
the  following  method  for  the  analysis  of  a  gas  mixture, 
which  provides  a  means  for  the  complete  determination 
of  carbon  monoxide  and  ethane.  The  gas  mixture  may 
contain  benzene,  or  benzole  vapor,  C6  HG ;  carbon  dioxide, 
CO2 ;  heavy  hydrocarbons  or  fixed  ill umin ants,  C2  H4 ; 
oxygen,  O;  carbon  monoxide,  CO ;  hydrogen,  H ;  meth- 
ane, CH4;  ethane,  C2  H6;  and  nitrogen,  N. 


68  .  TECHNICAL,  GAS  ANALYSIS. 

In  making  use  of  this  scheme  the  following  order  of 
analysis  should  be  observed : 

1.  Benzene  or  benzole  vapors  (C6H«),  absorbed  by  one 
cubic   centimeter   of  alcohol  in   mercury   pipette ;    after 
measuring  the  contraction  agitate  the  gas  with  one  cubic 
centimeter  of  water  to  remove  alcoholic  vapors. 

2.  Carbon  dioxide  (CO2),  absorbed  by  potassium  hy- 
droxide.    The   absorption   is  nearly  instantaneous,  one 
passage  of  the  gas  into  the  pipette  generally  sufficing. 

3.  Heavy  hydrocarbons  or  fixed  illuminants,  consist- 
ing principally  of  ethylene  (C2H4),  absorbed  by  afi  aque- 
ous solution  of  bromine.     Fuming  sulphuric  acid  gives  a 
slightly  greater  absorption,  but  bromine  is  far  more  con- 
venient and  sufficiently  accurate  for  most  purposes.    Time 
required  for  this  absorption,  three  minutes. 

4.  Oxygen  (O),  absorbed  by  phosphorus.     Time,  ten 
minutes.     Potassium  pyrogallate  may  be  used,  but  the 
first  offers  a  decidedly  more  elegant  method.     Time  with 
potassium  pyrogallate,  three  minutes. 

5.  Carbon  monoxide  (CO),  absorbed  by  a  solution  of 
cuprous  chloride.     An  alkaline  or  ammoniacal  solution  of 
cuprous  chloride  must  be  used,  since  the  absorption  of 
hydrogen  is  to  be  by  means  of  palladium,  which  would 
become   inactive    in   the  presence   of  hydrochloric   acid 
vapors.     In  making  the  cuprous  chloride  absorption,  it  is 
advisable  to  employ  two  pipettes,*  one  containing  a  solu- 
tion which  has  been  used  a  number  of  times,  and  the 
other  comparatively  fresh.     By  passing  the  gas  into  the 
first  and  agitating  therein  some  two  or  three  minutes,  and 
thus  removing  the  greater  part  of  the  carbon  monoxide, 
and  then  completing  the  absorption  by  a  passage  into  the 
second  pipette,  retaining  there  some  three  minutes.     This 
precaution  is  taken  owing  to  the  fact  that  the  affinity  of 
carbon  monoxide  for  cuprous  chloride  is  but  slight,  and 

*  Queen  &  Co.,  of  Philadelphia,  construct  an  apparatus  for  this  purpose,  con- 
sisting of  three  parts,  which  is  very  convenient. 


THE  HEMPEIy  APPARATUS.  69 

the  resulting  union  is,  in  consequence,  rather  unstable. 
Even  by  the  use  of  two  pipettes  traces  of  carbon  monoxide 
remain. 

The  residulal  gas  may  now  consist  of 

Hi       r^f\    /traces  remaining  unabsorbed\      i      fArr     _j_    r^  TT       i      -XT 
'     ^-U    Vby  cuprous  chloride  solution;    ""    W*4   "1"    v^2±16  "T    -^  • 

This  residual  gas  is  retained  in  the  cuprous  chloride 
pipette,  a  portion,  say  20  cubic  centimeters,  being  taken 
for  the  palladium  absorption.  In  the  palladium  reaction 
already  described  (the  20  cubic  centimeters  of  residual 
gas  is  simply  passed,  together  with  the  air  added,  over 
palladium),  are  removed  the  hydrogen  and  remaining 
traces  of  carbon  monoxide. 

The  combustion  of  the  two  is  represented  by  the  equa- 
tions: 

H2  +    (OJ,.  =  H,0         (i) 

CO  +    (02),  =*=  C02          (2) 

Inequation  i,  one  volume  of  hydrogen  uniting  with 
one-half  volume  of  oxygen,  condenses  to  water.  The 
contraction  is  therefore  one  and  one-half  volumes,  which 
is  one  and  one-half  times  the  hydrogen  burned,  or  i  %  H. 

In  equation  2,  one  volume  of  carbon  monoxide  uniting 
with  one-half  volume  of  oxygen,  contracts  to  one  volume 
of  carbon  dioxide.  The  contraction  is  therefore  one-half 
the  carbon  monoxide  burned,  or  y*  CO.  In  this  combus- 
tion there  is  formed  one  volume  of  carbon  dioxide  for 
each  volume  of  carbon  monoxide  burned,^  or  CO  =  CO.,. 
This  affords  a  means  of  determining  the  amount  of  carbon 
monoxide,  since  the  carbon  dioxide  may  be  absorbed  by 
potassium  hydroxide. 

Collecting,  we  have  for  the  total  contraction  due  to  the 
palladium  combustion: 

CL=  i%  H  +  %  CO,    (3)  and 

D!  =  CO  =  CO2,  (4)  in  which 

Ct  —  the  contraction  due  to  palladium  combustion, 


70  TECHNICAL,  GAS  ANALYSIS. 

D!  =  carbon  dioxide  formed  by  palladium  combustion, 
substituting  in  equation  3  the  value  of  CO  in  equation  4 

C,  =  i^H  +    J4D,     (5) 
and  by  simple  transposition 

2  d  -  D, 

H  = (6) 

3 

The  operation  thus  far  is  then  to  pass  the  sample  of 
residual  gas,  to  which  has  been  added  air,  over  palladium, 
causing  the  H  and  CO  to  be  burned.  The  products  of 
the  combustion  are  then  brought  back  and  the  volume 
measured,  showing  the  contraction,  which  is  designated 
G!  in  the  above  formulas.  The  gas  is  then  passed  into 
the  potassium  hydroxide  pipette  for  the  absorption  of  the 
carbon  dioxide  (formed  by  the  combustion  of  the  carbon 
monoxide).  The  gas  is  returned  to  the  measuring  burette 
and  the  contraction  due  to  the  carbon  monoxide  absorp- 
tion measured;  this  equals  Dx  in  the  above  formulas.  We 
now  know  the  hydrogen  and  the  carbon  monoxide  of  the 
residual  gas  sample. 

Another  portion  of  the  residual  gas  is  now  drawn  from 
the  cuprous  chloride  pipette  and  measured — say  about 
15  cubic  centimeters —  and  to  this  is  added  about  80  cubic 
centimeters  of  air,  enough  to  make  a  total  of  nearly  100 
cubic  centimeters.  The  mixture  is  transferred  to  the  ex- 
plosion burette  and  well  mixed.  It  is  then  exploded  over 
mercury.  The  resulting  contraction  we  will  call  C — 
and  is  due  to  the  following  reactions: 

The  carbon  monoxide  burning  to  carbon  dioxide 
(a)     CO  +  (O2)x  =  CO2         Contraction  =  ^  CO 

2 

The  volume  of  carbon  dioxide  formed  equals  the  volume 
of  carbon  monoxide  burned;  or,  CO2  =  CO. 

The  methane  burning  to  carbon  dioxide  and  water 
(6)     CHt  +  (O,),  =  C02  +  (H,0), 

Contraction  =  2  CH4 


HKMPKIy   APPARATUS.  71 

The  volume  of  carbon  dioxide  formed  equals  the  vol- 
ume of  the  methane  burned;  or,  CO2  =  CH± 

The  ethane  burning  to  carbon  dioxide  and  water 

(c)  C,H6+  (0?)8i=  (C02)2+  (H20)3 

Contraction  =  2%  C2  H6 

The  volume  of  carbon  dioxide  formed  equals  twice  the 
volume  of  ethane  burned;  or,  CO2  =  2C2  H6 
The  hydrogen  burning  to  water 

(d)  H2  +  (O2)1  —  H2O         Contraction  =  i^H 

2 

The  total  contractions  (C)  resulting  from  the  combus- 
tion of  residual  gas  in  the  explosion  pipette  is  then  the 
sum  of  the  contractions  resulting  from  the  reactions  ex- 
pressed by  equations  a,  b,  c,  and  d\  or, 

C  =  ^CO  +  2  CH,  +  2^C2H6  +  i#H         (7) 

The  total  volume  of  carbon  dioxide  (wre  will  designate 
this  D)  formed  by  the  combustion  of  residual  gas  in  the 
explosion  pipette,  would  equal  from  the  equations  a,  b,  c,  d 
D  =  CO  +  CH,  +  2  C2  H6       (8) 

The  procedure  is  then  to  ignite  the  sample  of  residual 
gas  in  the  explosion  pipette,  then  returning  to  the  meas- 
uring burette  to  determine  the  contraction  (C),  then 
transferring  the  gas  to  the  potassium  hydroxide  pipette  to 
absorb  the  carbon  dioxide  formed,  afterwards  measuring 
in  the  burette  the  volume  of  absorption  (D). 

Let  us  call 


+  2^  C2  Hti      (9) 
Let  us  call 
D  -  D,  =  F  =  (CO  +  CH4  +  2C.H6)  -  (CO) 

=  CH,  +  2C.H6         (10) 

Then  multiplying  F  by  2  and  subtracting  E  we  have 
2F  -  E=  (2CH,  +  4C2H0)  - 
(n) 


72  TECHNICAL  GAS  ANALYSIS, 

4F  —   2E 

or,     CaH6  = (12) 

3 
and  further,  we  have  from  equation  10 

CH4  =  F-2C2H6         (13) 

The  nitrogen  is  now  found  by  difference  making  all  the 
constituents  of  the  residual  gas  known. 

One  fact  to  be  noticed  is  that  F  or  D  —  Dt  cannot, 
under  any  circumstances,  be  less  than  J^E  or  *^(C  —  CJ, 
since,  if  in  equations 
(F  =  CH4  +  2C_Hti)  and  (E  ===  2CH,  +   2^C_HG) 

CH,  =  O,  then  F  ==  2C2H6  =  4/5  E ;         ( 14) 
or,  if  on  the  other  hand, 

CXHe  -  O,  then  F  -  CH,  ==  ^E         (15) 
Summing  up,  the  residual  gas  may  consist  of 

H  +  CO  +  CH4  +  C.H6  +  N 
By  the  palladium  combustion 

2C,  -  D, 

TT 

3 

in  which  CL  =  the  contraction  due  to  the  combustion  of 
the  hydrogen  and  carbon  monoxide  and  Dt  =  the  carbon 
dioxide  resulting  ==  the  carbon  monoxide  burned. 
By  the  explosion  over  mercury 

4F  —  2E 

CXH6  = ,   and 

3 

CH,  =  F  -  2C,H6 
in  which 

F  =  D  —  Dt  —  the  difference  between  the  volumes  of 
carbon  dioxide  formed  by  the  explosion  over  mercury 
(D)  and  the  palladium  combustion  (Dj). 

E  —  C  —  Ct  =  the  difference  between  the  contraction 
from  the  explosion  and  palladium  combustion. 


CHAPTER    VI.— MEASUREMENT    OF    GASES. 


CORRECTION    FOR    PRESSURE,    TEMPERATURE    AND    VAPOR     TENSION. 

Owing  to  the  fact  that  the  volume  of  a  gas  varies  with 
change  of  pressure  and  temperature,  it  is  necessary  to 
reduce  volumes  measured  under  different  conditions  to 
some  set  standard  in  order  that  a  true  comparison  may  be 
arrived  at.  Universal  custom  has  determined  this  standard 
as  760  millimeters  (29.92158  inches)  of  mercury  for  pres- 
sure, and  o°  C.  (32°  P.),  for  temperature;  hence  by  re- 
ducing to  these  conditions,  gases  of  similar  composition 
will  always  be  of  equal  mass  or  weight  per  unit  of  volume 
or  of  equal  volume  per  unit  of  mass  or  weight.  With 
this  understanding,  we  may  speak  of  one  liter  of  a  certain 
gas  as  always  having  the  same  mass  or  weight,  and  like- 
wise of  one  gram  as  always  having  the  same  volume, 
knowing  that  under  like  conditions  of  pressure  and  tern- 
perature  there  will  exist  a  constant  relation  between 
volume  and  mass. 

The  pressure  acting  upon  a  gas  is  generally  measured 
in  millimeters  or  inches  of  mercury:  that  is,  in  terms  of 
the  height  of  a  column  of  mercury  which  it  sustains; 
thus  the  atmospheric  pressure  is  read  from  a  barometer  as 
so  many  millimeters  or  inches  of  mercury^ 

In  determining  the  volume  of  a  gas,  therefore,  it  is 
necessary  to  consider  the  conditions  under  which  it  is 
measured.  If  in  an  open  vessel  or  in  a  vessel  over  a 
liquid,  as  mercury  or  water,  in  which  the  level  of  the 
liquid  is  the  same  inside  as  it  is  outside  the  vessel,  then 
a  reading  of  the  barometer,  giving  the  atmospheric  pres- 
sure, likewise  gives  the  pressure  acting  upon  the  gas. 

To  measure  a  gas  under  atmospheric  pressure  it  is  only 

(73) 


74 


TECHNICAL  GAS   ANALYSIS. 


A' 


300 


necessary  therefore,  to 
confine  it  in  a  vessel  over 
a  liquid  by  means  of  a 
level  tube,  and  adjust  the 
tube  so  as  to  bring  the 
level  of  the  liquid  both 
inside  the  vessel  and  in 
the  level  tube  to  the  same 
height,  for  should  the 
level  of  the  liquid  within 
the  vessel  be  higher  than 
in  the  tube,  the  gas  will 
be  under  diminished 
pressure,  and  if,  on  the 
other  hand,  it  is  lower 
than  in  the  tube,  it  will 
be  under  a  pressure 
greater  than  atmo- 
spheric, due  to  the  weight 
of  the  column  of  liquid 
above  its  level.  In  Fig- 
ure 23,  if  mercury  be 
used  for  the  confining 
liquid  in  a  level-tube  A' 
open  to  the  atmosphere, 
and  a  measuring  burette 
A  closed  at  the  upper  end 
by  a  pinch-cock,  then  it 
is  evident  that  with  the 
levels  of  the  mercury  at 
a'  and  a  in  the  level-tube 
and  measuring  burette  respectively,  the  gas  enclosed  in 
the  latter  above  the  mercury  is  not  exerting  as  great  a 
pressure  as  is  the  atmosphere  on  the  liquid  at  the  open 
end  of  the  level-tube  where  the  level  is  the  lowest.  The 


FIGURE  23. 


MEASUREMENT  OF  GASES.  75 

pressure  upon  the  gas  is  equal  in  this  case  to  the  atmo- 
spheric less  15  millimeters,  the  distance  between  the  levels, 
which  equals,  with  an  atmospheric  pressure  of  760  milli- 
meters, 745  millimeters  of  mercury  as  actual  pressure. 

Were  the  case  reversed,  that  is,  were  the  level  #15 
millimeters  lower  than  the  level  #',  then  the  pressure  on 
the  gas  would  equal  760+  15,  or  775  millimeters  oi 
mercury. 

If  water  is  employed  as  the  confining  liquid  instead  ot 
mercury,  it  will  be  necessary  to  determine  the  pressure  in 
terms  of  mercury  in  order  to  make  use  of  the  barometer 
and  standard  conditions.  Mercury  has  a  specific  gravity 
of  13.6;  that  is,  the  weight  of  a  given  volume  of  water 
is  but  V13.6  part  of  the  weight  of  an  equal  volume  of  mer- 
cury. In  the  foregoing  example,  had  the  liquid  been 
water,  with  the  same  pressure  acting  upon  the  gas,  there 
would  have  been  a  difference  of  level  of  about  204  milli- 
meters of  water,  which,  divided  by  13.6  would  give  the 
15  millimeters  of  mercury. 

Influence  of  Pressure  on  Volume.  What  is  known  as 
Boyle's  law  states  that  the  volume  of  a  perfect  gas  varies 
inversely  as  the  pressure  it  supports;  that  is,  the  greater 
the  pressure  the  less  the  volume.  The  following  example 
will  serve  to  illustrate  this: 

A  volume  of  ethylene,  C2H4,  measures  two  liters  under  a  pres- 
sure of  750  millimeters  of  mercury.  What  would  its  volume  be 
under  standard  conditions  of  pressure,  temperature  being  ne- 
glected? 

Standard  pressure  is  760  millimeters  of  mercury;  con- 
sequently we  are  to  determine  the  volume  under  an  in- 
creased pressure,  which,  by  the  law  of  Boyle,  will  give  us 
a  smaller  volume.     Thus: 
760  mm.  :  750  mm.  ::  2  litres  :  X  (the  required  volume) 

75° 

or,   2  X  —  X;  or,  X  =  1.9  liters; 

760 


7G  TECHNICAL  GAS  ANALYSIS. 

that  is,  the  volume  under  standard  conditions  of  pressure 
will  be  1.9  liters.     Conversely: 

A  volume  of  ethylene,  C2H4,  measures  1.9  liters  under  a  pressure 
of  760  millimeters  of  mercury.  What  would  its  volume  be  under 
a  pressure  of  750  millimeters,  temperature  being  neglected? 

It  is  here  required  to  ascertain  what  the  volume  of  a 
gas,  measured  under  standard  conditions  of  pressure, 
would  be  under  a  given  decreased  pressure,  which,  by  the 
law,  will  give  a  greater  volume.  Thus: 

750  mm.  :  760  mm.  ::  1.9  (liters)  :  X  (required  volume) 
760 

or,    1.9  X  =  X;  or,  X  =  2  liters. 

..."  750 

The  above  operations  may  be  stated  more  briefly  in  the 
following  rule: 

Multiply  the  volume  actually  measured  by  a  fraction  whose 
numerator  and  denominator  will  be  the  absolute  pressures,  the 
greater  of  which  will  be  the  denominator  or  numerator  according 
as  the  volume  is  to  be  decreased  or  increased,  which  may  be 
seen  by  an  inspection  of  the  problem  and  an  understanding  of 
Boyle's  law. 

Influence  of  Temperature  on  Volume.  Actual  experi- 
ment has  proven  that  all  gases  have  the  same  coefficient 
of  expansion  by  heat.  In  the  centigrade  scale  the  coef- 
ficient of  expansion  per  degree  is  0.003665,  or,  expressed 
in  fractional  form,  V273;  that  is,  the  pressure  being  con- 
stant, the  volume  of  a  perfect  gas  increases  V273  of  its 
volume  at  o°  C. ,  for  every  increase  in  temperature  of  i°  C., 
and  in  Fahrenheit  units  0.002036,  or  V491.2  of  its  volume 
at  32°  F.,  for  every  increase  of  i°  F.  Likewise  it  de- 
creases for  each  negative  degree. 

It  follows,  then,  that  the  volume  at 

i°  C.  —  vol.  at  o°  C.  -f-  ^3  (vol.  at  o°  C.)  =  -f£f  (vol.  at  o°  C.) 

2°  C.  =  vol.  at  o°  C.  +  vfa  (vol.  at  oc  C.)  =  fff  (vol.  at  o°  C.) 


MEASUREMENT  OF  GASES.  W 

3°  C.  ==  vol.  at  o°  C.  +  2T3-  (vol.  at  o°  C.)  —  fff  (vol.  at  o°  C.) 
t°  C.  =  vol.  at  o°  C.  +  273-  (vol.  at  o°  C.)  =  fyf  plus  *   (vol.  at  o°  C.) 
and  the  volume  at 

-  1°  C.  =  vol.  at  o°  C.  —  273  (vol.  at  o°  C.)  =  fff  (vol.  at  o°  C.) 

-  2°  C.  =  vol.  at  o°  C.  —  ?fa  (vol.  at  o°  C.)  =  ffj  (vol.  at  o°  C.) 
—  3°  C.  =  vol.  at  o°  C.  —  2^3  (vol.  at  o°  C.)  -    fyf  (vol.  at  o°  C.) 

and  at 

_  273°  =  vol.  at  o°  C  —  fYf  (vol.  at  o°  C.)  ==  ^  (vol.  at  o3  C.) 

that  is,  at  —  273°,  by  the  law,  the  gas  would  entirely 
disappear  or  be  of  no  volume,  which  would  be  impossible. 
To  account  for  this  apparent  discrepancy  in  the  law  gov- 
erning the  effect  of  temperature  on  perfect  gases,  we  find 
that  as  gases  approach  the  temperature  of  liquification, 
their  properties  change  from  those  of  a  perfect  gas  and 
thus  they  deviate  from  the  law.  In  order  to  facilitate 
computation,  however,  the  temperature  of  — 273°  C.  is 
considered  as  absolute  zero.  To  obtain  absolute  temper- 
ature, therefore,  add  273°  to  the  readings  of  the  Centigrade 
thermometer,  or  459.2°  (=  491.2  —  32) — generally  taken 
as  460° — to  the  readings  of  the  Fahrenheit  thermometer. 

From  the  foregoing  it  is  readily  seen  that  if  a  volume 
of  gas  measured  273  cubic  centimeters  at  o°  C.,  (which  is 
273°  C.  absolute  temperature),  and  was  raised  one  degree, 
bringing  the  absolute  temperature  to  274°  C.,  the  volume 
would  be  increased  y.273  of  the  volume  at  o°  C.,  or  the  vol- 
ume would  become  273+  1  =  274  cubic  centimeters;  and 
similarly,  if  raised  5°  C.,  the  volume  .would  become 
273  +  5  ~  278  cubic  centimeters.  We  may  therefore 
restate  the  law,  known  as  that  of  Charles,  as  follows: 

The  volume  of  a  gas  varies  directly  as  its  absolute  tem- 
perature; that  tSj  the  greater  the  temperature,  the  greater 
the  volume,  and  the  less  the  temperature,  the  less  the  volume. 

The  following  example  will  serve  to  illustrate  the  use 
of  this  law: 


78  TECHNICAL  GAS   ANALYSIS. 

A  volume  of  ethylene,  C2H4,  measures  two  liters  at  a  tempera- 
ture of  21°  C.  (69.8°  F.).  What  would  the  volume  be  under  stand- 
ard conditions  of  temperature,  pressure  being  neglected? 

Standard  temperature  is  o°  C. ;  consequently  we  are  to 
determine  the  volume  under  decreased  temperature,  which 
by  the  above  law,  will  give  a  decreased  volume.     Thus: 
Reducing  all  temperatures  to  absolute 

21°  C.  =  273  +  21  =  294°  C.  absolute 
o°  C.  =  273°  C.  absolute;  then, 

294°  C.  :  273°  C.   ::  2  (liters)  :  X  (required  volume) 

273 

or,   2  X  =  X  ;  or,  X  =  1.8  liters; 

294 

that  is,  the  volume  under  standard  conditions  of  temper- 
ature will  be  1.8  liters.     Conversely: 

A  volume  of  ethylene,  C2H4,  measures  1.8  liters  at  a  temperature 
of  o°  C.,  what  would  the  volume  be  under  a  temperature  of  21°  C., 
pressure  being  neglected? 

It  is  here  required  to  ascertain  what  the  volume  of  a 
gas,  measured  under  standard  conditions  of  temperature, 
would  be  at  a  given  increased  pressure,  which  by  the  law, 
will  give  an  increased  volume.     Thus: 
Reducing  all  temperatures  to  absolute 

o°  C.  =  273°  C.  absolute 

21°  C.  =  273  +  21  =  294°  C.  absolute;  then, 
273°  C.  :  294°  C.  ::   1.8  (liters)    :   X   (required  volume) 

294 

1.8  X  =  X ;  or,  X  =  2  liters ; 

273 

that  is,  the  volume  at  a  temperature  of  21°  C.,  will  be 
two  liters. 

jAfe  in  the  case  of  pressure,  operations  may  be  shortened 
by  the  following  rule: 

Multiply  the  volume  actually  measured  by  a  fraction  whose 
numerator  and  denominator  will  be  absolute  temperatures,  the 
greater  of  which  will  be  the  denominator  or  numerator,  according 


MEASUREMENT  OF  GASES.  *?9 

as  whether  the  volume  is  to  be  decreased  or  increased,  which  may 
be  seen  by  a  simple  inspection  of  the  problem  and  understanding 
of  Charles'  law. 

The  application  of  the  laws  for  both  pressure  and  tem- 
perature may  be  combined  in  one  operation.  Taking  the 
example: 

A  volume  of  ethylene,  C2H4,  measures  two  liters  under  a  pres- 
sure of  750  millimeters  of  mercury  and  at  a  temperature  of  21°  C., 
what  will  be  the  volume  under  standard  conditions  of  pressure 
and  temperature? 

Pressure  measured  under  =  750  millimeters 

Standard  pressure  =760  millimeters 

Temperature  measured  under  =  2i°C.  =  273  +  21  = 

294°  C.,  absolute. 
Standard  temperature  =  o°  C.  =  273°  C. 

As  the  pressure  is  to  be  increased,  its  effect  will  be  to 
diminish  the  volume.  As  the  temperature  is  to  be  de- 
creased, its  effect  will  be  to  diminish  the  volume  also, 
consequently  we  have 

750          273 

2  x  X  =  X;  or,  X  =  1.83  liters. 

760          294 

Vapor  Tension  of  Liquids.  The  pressure  due  to  the 
tendency  of  volatile  liquids  to  evaporate  is  termed  vapor 
tension. 

Vapor  escapes  from  the  surface  of  volatile  liquids  more 
or  less  readily  at  all  temperatures,  creating  a  pressure 
which  varies  with  the  temperature  and  is  dependent  upon 
the  nature  of  the  liquid.  With  the  same  liquid  however, 
under  like  conditions  of  temperature,  this  pressure  or  vapor 
tension,  as  it  is  termed,  remains  constant. 

With  increase  of  temperature  the  vapor  tension  becomes 
greater,  until  it  equals  the  external  or  atmospheric  pres- 
sure, when  what  is  termed  boiling  occurs — bubbles  of 
vapor  forming,  and,  in  bursting,  violently  agitating  the 
surface  of  the  liquid. 


80 


TECHNICAL,  GAS  ANALYSIS. 


Vapor  tension  varies  with  the  nature  of  the  liquid;  it 
is  consequent  then,  that  the  temperatures  at  which  different 
liquids  boil  will  vary  under  like  conditions  of  pressure. 

The  boiling  point  is  defined  above  as  the  temperature 
at  which  the  vapor  tension  becomes  equal  to  the  external 
pressure;  it  follows  then,  that  as  the  external  or  atmo- 
spheric pressure  varies,  the  boiling  point  also  changes. 
With  a  decrease  of  the  external  pressure  acting  upon  a 


FIGURE  24. 

liquid,  the  temperature  of  boiling  is  reduced,  since  the 
vapor  tension  need  not  become  as  high  to  equal  the  ex- 
ternal pressure,  and  similarly  with  increased  external 
pressure  the  boiling  point  is  raised. 

At  the  temperature  of  boiling  the  vapor  tei  sion  equals 


MEASUREMENT  OF  GASES.  31 

the  external  pressure;  this  fact  affords  a  ready  means  of 
determining  the  tension  of  different  liquids,  since  it  is  but 
necessary  to  note  the  external  pressure  (by  means  of  a 
barometer  if  atmospheric),  and  the  temperature  at  which 
the  liquid  boils. 

Effect  of  Vapor  Tension  on  Volume.  When  a  gas  is 
measured  over  a  liquid  such  as  water  or  mercury,  part  of 
the  gas  volume  may  be  vapor,  dependent  upon  the  tem- 
perature at  which  the  measurement  is  made.  To  assist 
in  separating  the  true  gas  volume  from  the  liquid  vapor, 
Table  I  has  been  compiled,  since  by  previously  de- 
termining the  vapor  tensions  of  the  liquids  employed 
for  different  temperatures,  we  may  easily  make  correc- 
tions for  the  measured  volumes.  The  accompanying 
illustration  will  serve  to  make  this  clear.  It  is  desired  to 
measure  the  volume  of  a  gas,  over  water,  in  the  closed  arm  A 
of  the  U  tube,  Figure  24.  The  water  over  which  the  meas- 
urement is  made  is  at  the  same  level  as  s  and  s'  in  both 
arms  of  the  tube,  indicating  an  external  pressure  equal  to 
that  within  the  closed  arm.  The  pressure  in  the  latter  is, 
however,  made  up  of  both  that  exerted  by  the  gas  volume 
and  that  of  the  vapor  tension.  If  we  let 
pa  —  the  atmospheric  pressure  in  millimeters  of  mer- 
cury =  the  barometer  reading, 

pt  —  the  tension  of  water  vapor  at  the  temperature  at 
which  the  measurement  was  made  (found  in  Table 
I  of  vapor  tensions), 
p  —  the  net  or  true  pressure  exerted  by  the  gas  to  be 

measured. 
Then, 

P  (true  pressure)  =  Pa  (atmospheric  pressure) 

—  Pt  (vapor  tension). 

Consequently,  in  taking  account  of  the  tension  of  vapor 
in  the  measurement  of  a  gas  volume,  it  is  but  necessary 
6 


82  TECHNICAL  GAS   ANALYSIS. 

to  find  the  true  pressure  (atmospheric  less  pressure  due  to 
vapor  tension)  for  use  in  reducing  to  standard  conditions. 

The  true  or  net  pressure  will,  of  course,  always  be  less 
than  atmospheric  or  that  indicated  by  the  barometer. 

L,et  us  consider  the  following  example: 

A  volume  of  ethyleue,  C2H4)  measured  over  water,  under  a 
pressure  of  750  millimeters  of  mercury,  and  at  a  temperature  of 
21°  C.,  gave  a  volume  of  2  liters.  What  would  its  volume  be 
under  standard  conditions  of  pressure  and  temperature,  and  when 
making  correction  for  vapor  tension  ? 

We  have: 
Pressure  measured  under...  =          750  mm.  of  mercury, 

Standard  pressure =          760  mm.  of  mercury, 

From  table,  vapor  tension  of 

water  at  21°  C =     18.495  mm.  of  mercury, 

Pressure  corrected  for  vapor 

tension  =  750  —  18.495...  =  731.505  mm.  ot  mercury, 
Temp'ture  measured  under 

=  21°  C.,  or  273  +  21...  =  294°  C.,  absolute, 
Standard  temp  'at  ure  =  o°C.  =  273°  C. ,  absolute. 

We  have  then: 

750          273 
2  X  -      -  X  —  -  =  X,  or  X  =  1.83  liters 

760          294 

as  the  volume  when  the  pressure  is  uncorrected  for  vapor 
tension;  and 

731.505         273 
2X-  -X-     -  =  X,  or  X  =  1.78  liters 

760  294 

as  the  volume  when  the  pressure  is  corrected  for  vapor 
tension. 

1.83—  i. 78  =  0.05  liters  =  the  difference  due  to  the 
presence  of  water  vapor,  which,  had  it  not  been  taken 
into  account,  would  have  been  considered  as  gas. 

The  foregoing  tends  to  emphasize  the  necessity  of  mak- 
ing corrections  for  vapor  tension  where  great  accuracy  is 
required  in  the  measurement  of  gas  volume. 


MEASUREMENT   OF   GASES.  83 

When  a  gas  is  measured  over  a  liquid  not  easily  vola- 
tile at  ordinary  temperatures,  such  as  mercury,  it  may 
be  saturated,  previous  to  measurement,  with  water  vapor 
by  simply  introducing  a  drop  or  so  of  water. 

When  the  measurement  is  made  over  water,  the  gas 
will  always  be  saturated.  This  is  a  necessary  condition 
in  order  that  use  may  be  made  of  the  tables  of  vapor  ten- 
sion, the  tensions  being  known  only  for  saturated  gases. 

In  measuring  perfectly  dry  gases  over  mercury  at 
ordinary  temperatures,  no  correction  for  vapor  tension 
need  be  made,  since  the  tension  of  vapor  of  mercury  is 
but  slight,  and  furthermore,  is  offset  by  a  like  tension  of 
the  mercury  of  the  barometer  at  atmospheric  pressures. 
It  is  but  necessary  in  this  case  then,  to  simply  make  cer- 
tain that  both  the  barometer  and  gas  volume  being  meas- 
ured, are  subject  to  like  temperature  and  pressure,  when 
the  mercury  of  the  barometer  will  stand  lower  on  the 
scale  by  just  the  amount  of  the  tension  of  mercury,  due 
to  the  temperature  acting  on  it,  giving  a  reading  there- 
fore, equal  to  the  true  pressure  to  which  the  gas  volume 
is  subject. 

In  event  of  gases  being  measured  over  mercury  at  tem- 
peratures higher  than  the  barometer  is'  subject  to,  then 
the  difference  of  vapor  tension  at  the  two  temperatures 
(that  of  the  barometer  and  that  of  the  gas  volume)  should 
be  subtracted  from  the  atmospheric  pressure  to  determine 
the  true  pressure. 

The  expansion  of  mercury  at  high  temperatures  must 
also  be  taken  into  account.  The  preferable  method  is, 
therefore,  to  keep  the  temperatures  of  both  the  gas  volume 
(to  be  measured  over  mercury)  and  of  the  barometer  the 
same  whenever  possible,  thus  obviating  all  necessity  for 
correction  for  the  tension  or  expansion  of  the  mercury. 

Table  III  gives  the  tension  of  mercury  vapor  at  various 
temperatures. 


CHAPTER    VII. 


PROPERTIES    OF    GASES.— PREPARATION    OF    REAGEXTS    EMPLOYED. 

Properties  of  gases.  CARBON  DIOXIDE.  Synonyms: 
carbonic  acid  gas,  choke-damp,  after-damp,  etc.  Formula 
CO2.  Molecular  mass  (generally  termed  weight),  44; 
more  correctly,  according  to  atomic  weights  of  Prof.  F. 
W.  Clarke,  39.002.  Specific  gravity  compared  to  air, 
1.5290.  Weight  of  one  liter,  1977  grams;  weight  of  one 
cubic  foot,  0.12343  pounds. 

An  irrespirable,  colorless  gas,  denser  than  air,  having  a 
pungent  odor  and  acid  taste.  It  is  fatal  to  animal  life; 
extinguishes  combustion.  At  standard  conditions  of 
temperature  and  pressure  (o°  C.  and  760  millimeters  of 
mercury)  water  absorbs  or  dissolves  about  one  volume  of 
carbon  dioxide;  as  the  pressure  increases,  temperature 
remaining  constant,  a  greater  absorption  takes  place,  an 
additional  volume  being  absorbed  for  each  atmosphere  of 
pressure  added.  Carbon  dioxide  becomes  liquid  at  a  pres- 
sure of  38.5  atmospheres  and  o°  C.,  with  a  specific  gravity 
of  0.923.  At  —65°  C.  the  liquid  solidifies  to  a  trans- 
parent mass  like  ice.  A  temperature  of  — 140°  C.  may 
be  obtained  by  means  of  frozen  carbon  dioxide  moistened 
with  ether  and  placed  in  a  vacuum. 

Preparation:  Carbon  dioxide  may  be  prepared  by  the 
action  of  an  acid  upon  some  carbonate: 

CaC03  +  (HN03)2  =  Ca(NO3)2  +  H2O  +  CO2 

Calcium  Nitric  Acid  Calcium  Water          Carbon 

Carbonate  Nitrate  Dioxide 

ETHYLENE.  Synonyms:  olefiant  gas,  ethene,  hydro- 
gen di-carbide.  Formula  C2H4.  Molecular  mass,  28; 
according  to  Prof.  F.  W.  Clarke,  27.9472.  Specific 
gravity  compared  to  air,  0.9847.  Weight  of  one  liter, 
1.273  grams;  weight  of  one  cubic  foot,  0.07949  pounds. 

(84) 


PROPERTIES  OF  GASES.  85 

An  irrespiralbe,  colorless  gas,  with  odor  of  ether.  Sol- 
uble in  about  eight  times  its  volume  of  water.  Combus- 
tible, emitting  a  brilliant  white  flame  when  burning  in 
air,  and  evolving  much  smoke.  Mixed  in  the  proportion 
shown  in  formula  below  (one  volume  of  ethylene  to  three 
volumes  of  oxygen),  explodes  violently  on  ignition.  At 
9.8  millimeters  pressure,  its  evaporation  produces  a  tem- 
perature of  —  1 50. 4  degrees.  It  is  the  principal  constituent 
of  the  fixed  illuminants  or  heavy  hydrocarbons. 

The  reaction  with  oxygen  is: 

CXH4  +  (0,),  =  (CO,).  +  (HaO), 

One  volume  of  ethylene  +  three  volumes  of  oxygen 
unite  to  form  two  volumes  of  carbon  dioxide  and  two 
volumes  of  water,  but  the  water  may  be  considered  as 
possessing  no  volume  (owing  to  contraction  in  changing 
from  a  gaseous  to  liquid  form),  consequently  the  contrac- 
tion due  to  the  combustion  of  ethylene  is  2CjH4;  i  volume 
+  3  volumes  =  4  volumes;  4 — 2  =  2  volumes  contraction, 
or,  for  every  volume  of  ethylene  burned  there  is  a  result- 
ing contraction  of  two  times  the  volume  of  ethylene,  or, 
contraction  equals  2C2H4.  A  reference  to  the  reaction 
also  shows  that  two  volumes  of  carbon  dioxide  are  formed 
for  each  volume  of  ethylene  burned,  or  the  carbon  dioxide 
formed  equals  two  times  the  ethylene  burned;  CO,=  2C2H4. 

Preparation:     Ethylene  may  be  prepared  by  the  action 

T 

of  sulphuric  acid  upon  alcohol:     C2H6O  =  C2H4  +  H.,0. 

OXYGEN.  Symbol  O.  Atomic  mass,  16;  or,  according 
to  Prof.  F.  W.  Clarke,  15.9633.  Valence  II.  Molecular 
mass,  32;  or,  according  to  the  atomic  weight  of  Prof.  F. 
W.  Clarke,  31.9266.  Specific  gravity  compared  to  air, 
1.1051.  Weight  of  one  liter,  1.4298  grams.  Weight  of 
one  cubic  foot,  0.08948  grams. 

Oxygen  is  respirable  when  pure,  accelerating  the  respi- 
ration; a  colorless,  odorless,  tasteless  gas,  of  greater 


86  TECHNICAL  GAS  ANALYSIS. 

density  than  air,  and  slightly  soluble  in  water,  100  vol- 
umes of  water  at  o°  C.  taking  up  4.  i  volumes  of  oxygen. 
The  union  of  any  element  \vith  oxygen  is  what  is  generally 
implied  by  combustion.  The  action  of  oxygen  in  air  is 
much  less  active  in  such  union  than  when  pure,  owing  to 
the  dilution  with  nitrogen.  Combustion  with  oxygen  is 
attended  with  light  and  heat.  Oxygen  becomes  liquid  at 
20  atmospheres  of  pressure,  at  a  temperature  of  — 136°  C. 
Preparation:  Oxygen  may  be  prepared  by  heating  po- 
tassium chlorate,  mixed  with  one-quarter  of  its  weight  of 
manganese  dioxide: 

(K  CL  0,)a  +  MNOa  -  (K  CL)a  +  MNOa  +  (O2)8 

Potassium  Manganese          Potassium         Manganese        Oxygen 

Chlorate  Dioxide  Chloride  Dioxide 

Unchanged 

CARBON  MONOXIDE.  Synonyms:  carbonic  oxide,  car- 
bonyl.  Formula,  CO.  Molecular  mass,  28;  according 
to  Prof.  F.  W.  Clarke,  27.9369.  Specific  gravity  com- 
pared to  air,  0.9674.  Weight  of  one  liter,  1.251  grams. 
Weight  of  one  cubic  foot,  0.07810  pounds. 

It  is  an  irrespirable,  colorless  gas,  with  suffocating 
odor.  One  per  cent,  in  air  proves  fatal  to  life.  Combus- 
tible, burning  with  a  blue  flame.  It  is  a  constituent  of 
water  gas,  made  by  passing  steam  over  incandescent  fuel, 
and  has,  in  this  connection,  been  the  topic  of  much  dis- 
cussion and  even  legislative  interference,  owing  to  the 
difficulty  of  detection  and  fatal  effects  on  life.  It  is  con- 
densible  to  a  liquid  at  —139.5°  C.,  and  35.5  atmospheres. 

The  reaction  with  oxygen  is  CO  +  (Oa)j  =  CO.. 

One  volume  of  carbon  monoxide  combining  with  one- 
half  volume  of  oxygen  forms  one  volume  of  carbon  diox- 
ide; or,  the  contraction  is  i}4  —  i  =  /^  or  J^CO.  The 
carbon  dioxide  formed  equals  the  volume  of  carbon  mon- 
oxide burned,  or  CO2  =  iCO. 

Preparation:  Carbon  monoxide  may  be  prepared  by 
heating  oxalic  acid  with  strong  sulphuric  acid: 


PROPERTIES  OF   GASES.  87 

H.2C2O4  =  H2O  +  CO2  +  CO 

•  Oxalic  Water         Carbon       Carbon 

Acid  Dioxide      Monoxide 

As  seen,  CO2  is  also  present  in  the  products,  but  can  be 
removed  by  treating  with  potassium  hydroxide,  absorbing 
it  as  in  gas  analysis. 

NITROGKN.  Symbol  N.  Atomic  mass,  14;  according 
to  Prof.  F.  W.  Clarke,  14.01.  Valence  I,  III  and  V. 
Molecular  mass,  28;  according  to  atomic  mass  of  Prof.  F. 
W.  Clarke,  28.02.  Specific  gravity  compared  to  air, 
0.9714.  Weight  of  one  liter,  1.2561  grams;  weight  of 
one  cubic  foot,  0.07842  pounds. 

Nitrogen  is  an  irrespirable  (it  exerts  no  injurious  action 
upon  animal  tissue,  but  does  not  support  life),  colorless, 
odorless,  and  tasteless  gas  of  less  density  than  air,  slightly 
soluble  in  water,  2.5  volumes  being  absorbed  by  100  of 
water.  It  is  inert  as  regards  combustion,  uniting  with 
oxygen  only  at  an  elevated  temperature.  Cooled  to  —  1 50° 
C.,  in  liquid  ethylene,  boiling  under  a  pressure  of  10 
millimeters;  nitrogen  is  liquefied  by  a  pressure  of  about 
30  atmospheres. 

Preparation:  ,  Nitrogen  may  be  prepared  by  heating 
ammonium  nitrate: 

(NH4)  NO,  =  (HaO)a  +  Nf 

Ammonium  Nitrite  Water  Nitrogen 

HYDROGEN:  Symbol,  H;  atomic  mass,  i;  Valence,  I; 
molecular  mass  2;  specific  gravity  compared  to  air,  0.0695; 
weight  of  one  liter,  0.089578  grams;  weigh't  of  one  cubic 
foot,  0.005592. 

An  irrespirable,  colorless,  odorless  and  tasteless  gas, 
and  the  lightest  form  of  matter  known,  being  about  14.43 
times  lighter  than  air.  It  is  slightly  soluble  in  water,  1.9 
volumes  being  absorbed  by  100  volumes  of  water.  Heated 
to  about  500°  C.,  it  is  combustible,  combining  with  oxygen 
with  evolutions  of  light  and  heat.  It  produces  a  pale, 


80  TECHNICAL  GAS   ANALYSIS. 

bluish  flame,  which  becomes  bright  with  increasing  pres- 
sure. Hydrogen  in  burning  evolves  34,462  calories  per 
kilogram.  Cooled  in  boiling  nitrogen  to  —  213°  C.,  under 
a  pressure  of  160  atmospheres,  hydrogen  has  been  brought 
to  a  colorless,  transparent  liquid. 
The  reaction  with  oxygen  is: 

H.  +  (02),  =  H20 

"2" 

One  volume  of  hydrogen  combining  with  one-half  vol- 
ume of  oxygen  forms  water,  the  volume  of  the  latter  being 
neglected  for  reasons  heretofore  given;  hence  we  have 
i  volume  +  YZ  volume,  or  iJ/2  volumes  contracting  to 
zero  volumes;  or,  the  amount  of  contraction  equals  ij4 
volumes,  which  is  \yz  times  the  amount  of  hydrogen 
burned.  (i)^H).' 

Preparation :  Hydrogen  may  be  prepared  by  the  action 
of  zinc  upon  an  acid,  as  sulphuric  acid: 

Ha(SO4)    +    Zn   =    Zn(S04)    +    H2 

Hydrogen  Zinc  Zinc  Free 

Sulphate  or  Sulphate  Hydrogen 

Sulphuric  Acid 

METHANE:  Synonyms,  marsh  gas,  fire-damp,  hydro- 
gen carbide;  formula,  CH4;  molecular  mass,  16;  according 
to  Prof.  F.  W.  Clarke,  15.9736.  Specific  gravity  com- 
pared to  air,  0.5560;  weight  of  one  liter,  0.7x9  grams; 
weight  of  one  cubic  foot,,  0.04488  pounds. 

An  irrespirable,  colorless,  odorless,  tasteless  gas,  and  is 
the  next  lightest  gas  to  hydrogen.  It  is  slightly  soluble 
in  water;  combustible,  emitting  a  pale,  faintly-luminous 
flame  when  burning  in  air.  Mixed  with  oxygen  in  the 
proportions  expressed  in  the  reaction  below,  two  volumes 
of  oxygen  or  about  ten  volumes  of  air,  forms  an  explosive 
mixture,  often  the  cause  of  serious  accidents  in  coal  mines, 
where  it  collects,  together  with  other  explosive  gases. 

The  reaction  with  oxygen  is: 

CH,  +    (02)2  =  C02  +.(HaO)a 


PROPERTIES  OF  GASES.  09 

One  volume  of  methane  combining  with  two  volumes 
of  oxygen,  forms  one  volume  of  carbon  dioxide  and  water. 
The  volume  of  water  being  neglected,  we  have  i  volume 
+  2  volumes,  or  3  volumes  contracting  to  i  volume;  or, 
the  amount  of  contraction  equals  2  volumes,  which  is  2 
times  the  volume  of  methane  burned.  (2CHJ.  Further- 
more, for  each  volume  of  methane  burned  there  is  one 
volume  of  carbon  dioxide  formed,  or,  CO2  =  CH4. 

Preparation.  Methane  may  be  prepared  by  heating 
sodium  acetate  in  presence  of  sodium  hydroxide: 


^^   \    ^-TLj  ,  JWi-.f     **  nf^   \   \J±\&          i 

C0  I  ONa     +     H    S   °  C°  1  ONa     + 

Sodium  Sodium  Sodium  Methane 

Acetate  Hydroxide  Carbonate 

Preparation  of  the  Reagents  Employed.  POTASSIUM 
HYDROXIDE.  Dissolve  500  grams  of  commercial  hydrox- 
ide (which  has  not  been  purified  by  alcohol)  in  one  liter 
of  pure  water.  It  is  ready  for  use  as  soon  as  made.  Ca- 
pacity :  One  cubic  centimeter  absorbs  40  cubic  centimeters 
of  carbon  dioxide. 

SODIUM  HYDROXIDE.  Make  a  saturated  solution  of 
the  commercial  hydroxide  in  pure  water. 

BARIUM  HYDROXIDE.  Make  a  saturated  solution  of 
barium  oxide  in  water,  (the  barium  oxide  slakes). 

Of  these  reagents,  the  first  is  preferable  owing  to  its 
rapidity  of  action,  the  second  to  its  cheapness,  and  the 
third  to  its  accuracy  where  the  carbon  dioxide  is  in  small 
quantities. 

BROMINE  WATER.  Made  by  adding  a  little  bromine 
to  a  liter  of  water,  very  little  being  required  to  saturate 
the  water,  causing  it  to  give  off  bromine  vapors. 

POTASSIUM  PYROGAI.LATE  To  50  grams  of  pyrogallic 
acid  add  1000  cubic  centimeters  of  potassium  hydroxide 
as  made  above.  Keep  well  corked  owing  to  its  affinity 


90  TECHNICAL,  GAS  ANALYSIS. 

for  the  oxygen  of  the  air.  It  is  ready  for  us  a  as  soon  as 
made.  Capacity:  One  cubic  centimeter  absorbs  two 
cubic  centimeters  of  oxygen. 

CUPROUS  CHLORIDE.  Place  in  a  liter  reagent  bottle 
300  grams  of  copper  oxide,  and  on  this  arrange  a  bunch 
of  copper  wire  to  reach  the  entire  length  of  the  bottle. 
Then  fill  with  hydrochloric  acid  (specific  gravity  i.io). 
The  bottle  is  shaken,  well  corked  to  prevent  the  absorption 
of  oxygen,  and  allowed  to  stand  in  the  dark  till  psrfectly 
clear,  when  it  is  ready  for  use.  Exposure  to  light  will 
cause  it  to  assume  a  brownish  color,  which  does  not  affect 
its  action,  however.  Capacity:  One  cubic  centimeter 
absorbs  one  cubic  centimeter  of  carbon  monoxide. 


TABLE  I. 


Tension  of  water  vapor'in  millimeters  of  mercury  for  different 
temperatures.  Also  the  weight  in  grams  of  the  vapor  contained 
in  a  cubic  meter  of  air  when  saturated. 


Degrees 
Centigrade 

Tension  in 
Millimeters 

n* 

Oa> 

If 

Cft 

Degrees 
Centigrade 

Tension  in 
Millimeters 

Weight 
in  Grams 

Degrees 
Centigrade 

Tension  in 
Millimeters 

Weight 
in.  Grams 

—2O. 

0.927 

5.4 

6.717 

13.2 

11.309 

—  10. 

2.093 

5-6 

6.810 

13-4 

11.456 

—  2. 

3-955 

5-8 

6.904 

13-6 

11.605 

—  r.8 

4.016 

6. 

6.998 

7-3 

13.8 

11-757 

—  1.6 

4.078 

6.2 

7-095 

14. 

11.908 

12. 

—1.4 

4.140 

6.4 

7-193 

14.2 

12.064 

—  1.2 

4.203 

6.6 

7.292 

14.4 

12.220 

—  I. 

4.267 

6.8 

7-392 

14.6 

12.378 

—0.8 

4.331 

7- 

7-492 

7-7 

14.8 

12.538 

—0.6 

4-397 

7-2 

7-595 

15- 

12.699 

12.8 

—0.4 

4-463 

7-4 

7.699 

15.2 

12.864 

—  0-2 

4o3i 

7-6 

7.840 

15-4 

13.029 

0. 

4.600 

7.8 

7.910 

15.6 

13.197 

+0.2 

4.667 

8. 

8.017 

8.1 

15-8 

I3.366 

+0.4 

4.733 

8.2 

8.126 

16. 

13.536 

13-6 

-fa  6 

4.801 

8.4 

8.236 

16.2 

13.710 

-f-o.8 

4.871 

8.6 

8.347 

16.4 

13.885 

-4-1. 

4.940 

8.8 

8.461 

16.6 

•    14.062 

-fl.2 

5.011 

9- 

8-574 

8.8 

16.8 

14.241 

+  1.4 

5.082 

9-2 

8.690 

17- 

14.421 

H.5 

+  1.6 

5.155 

9.4 

8.807 

17.2 

14.605 

+  1.8 

5.228 

9-6 

8.925 

17.4 

14.790 

+  2. 

5.302 

9.8 

9.045 

17.6 

14-977 

+  2.2 

5.378 

10. 

9.165 

9-4 

17.8 

15.167 

+  2.4 

5-454 

10.2 

9.288 

18. 

15-357 

I5.I 

+  2.6 

5.530 

10.4 

9.412 

18.2 

15.552 

+  2.8 

5.608 

10.6 

9-537 

18.4 

15-747 

+3. 

5.687 

10.8 

9-665 

18.6 

15-945 

+3-2 

5-767 

ii. 

9-792 

10. 

i&i 

16.145 

+3.4 

5.848 

II.  2 

9-923 

19- 

16.346 

16.2 

+3-6 

5-930 

II.4 

10.054 

19.2 

16.552 

3-8 

6.014 

ir.  6 

10.187 

19.4 

16.758 

4- 

6.097 

ii.  8 

10.322 

19.6 

16.967 

4.2 

6.183 

12. 

10.457 

10.6 

19.8 

17.179 

4.4 

6.270 

12.2 

10.596 

20. 

17.391 

17.2 

4.6 

6.350 

12.4 

io.734 

20.2 

17.608 

4.8 

6.445 

12.6 

10.875 

20-4 

17.826 

5- 

6-534 

6.8 

12.8 

10.019 

20.  6 

18.047 

5-2 

6.625 

13. 

11.162 

"•3 

!      20.8 

18.271 

(91) 


TABL,E  I. —CONTINUED. 


Tension  of  water  vapor  in  millimeters  of  mercury  for  different 
temperatures.  Also  the  weight  in  grams  of  the  vapor  contained 
in  a  cubic  meter  of  air  when  saturated. 


Degrees 
Centigrade 

Tension  in 
Millimeters 

|l 

11 

t/j 

Degrees 
Centigrade 

Tension  in 
Millimeters 

Weight 
in  Crams 

Decrees 
Centigrade 

Tension  in 
Millimeters 

Si 

3€ 

3% 

m 

21. 

18.495 

lS.2 

27.6 

27.455 

99-3 

741.16 

21.2 

18.724 

27.8 

27.778 

99-4 

743-  S3 

21.4 

18.954 

28. 

28.101 

27. 

99-5 

746.5 

21.6 

19.187 

28.2 

28.433 

9>6 

749.18 

21.8 

19.423 

28.4 

28.765 

99-7 

751.87 

22. 

I9-659 

19-3 

28.6 

29.101 

99-8 

754.57 

22.2 

19.901 

28.8 

29.441 

99.9 

757.28 

22.4 

20.143 

29. 

29.782 

28.6 

100. 

760. 

22.6 

20.389 

29.2 

30.I3I 

1  00.  1 

762.73 

22.8 

20.639 

29.4 

3°-479 

TOO.  2 

765.46 

23. 

20.888 

20.4 

29.6 

30-833 

100.3 

768.20 

23.2 

21.144 

29.8 

31.190 

100.4 

771.95 

23-4 

21.400 

30. 

3L548 

29.2 

100.5 

773.71 

23.6 

21.659 

3f. 

33.405 

100.6 

776.48 

23.8 

21.921 

32. 

35-359 

100.7 

779.26 

24. 

22.184 

21.5 

33- 

37.4io 

100.8 

782.04 

24.2 

22.453 

34. 

39.565 

100.9 

784.83 

24.4 

22.723 

35- 

41.827 

101. 

787.63 

24.6 

22.996 

40. 

54.906 

105. 

960.41 

24.8 

23-273 

45. 

7L39I 

no. 

1075-37 

25. 

23-550 

22.9 

50. 

91.982 

120. 

1491.28 

25.2 

23-834 

55- 

117.478 

I30. 

2030.28 

25-4 

24.119 

to. 

148.791 

I4O. 

2717.63 

25.6 

24.406 

65- 

186.945 

150. 

3581.23 

25.8 

24.697 

70. 

233-C93 

160. 

4651.62 

26. 

24.988 

24.2 

75- 

288.517 

170. 

5961.66 

26.2 

25.288 

80. 

354.643 

1  80. 

7546.39 

26.4 

25.588 

So- 

433-04I 

190. 

9442.70 

26.6 

25.891 

90. 

525-450 

200. 

11688.96 

26.8 

26.198 

95- 

633.778 

2  2O. 

17390. 

27. 
27.2 

26.505 
26.820 

25.6 

99- 
99.1 

733-21 
735.85 

224.7 

25  atmos- 
pheres 

27.4 

27.136 

992 

738.5 

(92) 


TABLE  II. 


FRENCH  MEASURE. 

One  Millimetre  (roV^  of  a  metre) 0.039370  inches 

One  Centimetre  (T JQ  of  a  metre)  .    .    .    f   .   .  0.393704  inches 

One  Decimetre  (^  of  a  metre  j 3-937O43  inches 

One  Metre  (unit  of  length) 39.370432  inches 

One  Decametre  (10  metres) 393.704320  inches 

One  Hectometre  (100  metres) 3937.043196  inches 

One  Kilometre  (1000  metres) 39370.431960  inches 

One  Myriametre  (10,000  metres) 393704.319600  inches 

or,  6  miles,  376  yards,  o  feet  and  8j5g  inches 


TABLE  III. 


TENSION   OF   MERCURY  VAPOR. 


Degrees 
Centi- 
grade 

Tension  in 
Millimetres 

Degrees 
Centi- 
grade 

Tension  in 
Millimetres 

Degrees 
Centi- 
grade 

Tension  in 
Millimetres 

100 

0-75 

I  So 

11.00 

260 

96.73 

110 

1.07 

190 

14.84 

270 

123.01 

120 

1-53 

200 

19.90 

280 

155.17 

I30 

2.18 

210 

2635 

290 

194.46 

140 

3.06 

220 

34-70 

300 

242.15 

150 

4.27 

230 

45-35 

310 

299.69 

1  60 

5-9° 

240 

58.82 

320 

368.73 

170 

8.09 

250 

75-75 

330 

450.91 

(93) 


INDEX. 


Absorption    pipette,   manipulation    of 

the,  54-56 
After-damp,  84 
Analysis  of  a  gas,  12-16 

coal  gas,  35-38,  57-6i 

scheme  for  the,67~72 
Barium  hydroxide,  preparation  of,  89 

use  of,  as  a  reagent,  13 
Benzene  or  benzene  vapors,  absorption 

of,  68 
Boiling,  definition  of,  79 

point,  definition  of,  80 
Boyle's  law,  75 
Bromine  water.  14 

preparation  of,  89 
Burette,  measuring,  9 

to  calibrate  a,  9,  10 
Carbon  dioxide,  absorption  of,  68 

*     with  a  reagent,  13 

amount  of,  formed  by  the 

combustion    of    the   gas 

residue,  37 

determination  of,  13,  14,  21, 

22,  29,  30 
percentage  of  in  coal  gas, 

57,58 
properties  and  preparation 

of,  84 
monoxide,  absorbent  for,  15 

absorption  of,  65,  66,  68,,  69 
determination  of,  15,  16,  22, 

31 
percentage  of,  in  coal  gas. 

36,58 
properties  and  preparation 

of,  86,  87 
Carbonic  acid  gas,  84 

oxide,  86,  87  > 
Carbouyl,  86,  87  *« 
Charles'  law,  77-79  . 
Chimney  gases,  apparatus  for,  7 

examination  of,  by  means 
of  the  Orsat  apparatus, 
17-23 

Chloride,  cuprous,  15 
Choke  dump,  84 
Coal  gas,  analysis  of,  35-38,  57-61 

percentage  of  carbon  dioxide 

in,  57,  58 

monoxide 

^          A  36'  58 
heavy  hydrocar- 

carbons  in,  58 
illumiiiants   in, 

35,  36  . 

oxygen  in,  36,58 
scheme   for  the  analysis  of, 
67-72 


Collection  tubes,  i,  2 

Compound  pipettes,  manipulation  of 

,the,  57 

Conduit,  currents  in  a,  5,  6 
Correction   for  pressure,   temperature 

and  vapor  tension,  73-75 
Cuprous  chloride,  15 

absorption  method  of  mak- 
ing the,  68,  69 
preparation  of,  90 
Double  absorption  pipette,  45 

lor  solid    and    li- 
quid    reagents, 
45-47 
Dowson  producer  gas,  partial  analysis 

of,  15,  16 
Elliott  apparatus.  24-38 

description  of,  24-26 
errors    in   the    results    ob- 
tained with  the,  24 
operation  with  the,  26-29 
principal    inuovatiou  with 

the,  24 
table  of  analyses  made  with 

the,  38 

Ethene,  84,  85 
Ethylene,  14 

absorbent  for,  14 

pipette,  48 

properties   and   preparation  of, 

84,  85 
Explosion  pipette,  49,  50 

with  electrodes  for  the  de- 
composition of  water, 

Fire  damp.  88.  89 

Fisher's  modification  of  the  Orsat  ap- 
paratus, 18,  19 
Flue,  currents  in  a,  5,  6 
gas.  analysis  of,  38 
Fractional  combustion    of  hydrogen, 

6 1-66 

French  measures,  table  of,  93    • 
Furnace  gases,  apparatus  for,  7 

examination  of,  by  means 
of  the  Orsat  apparatus, 
17-23 

piping  for  running  into  the,  5 
Gas,  analysis  of  a  12-16 

technical,  7-16 

apparatus  for,  7 

apparatus  for  obtaining  a  rough 
estimate  of  the  constituents  of 
a,  7-1 i 

collection  of  samples  of,  1-6 
composition,  alteration  of  the,  by 
iron  piping  raised  to  a  tempera- 
ture of  redness,  5 


(94) 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 


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